Working with Digital Signature

26 Apr 202224 minutes to read

Adding a digital signature

The Essential PDF allows you to add a digital signature to the PDF document. To add a digital signature, you need a certificate with private keys. The Essential PDF provides support for digital signature by using the PFX files, Hardware Security Module (HSM), Online Certificate Status Protocol (OCSP), Certificate Revocation List (CRL), Windows Certificate Store, and supports signatures using the Elliptic Curve Digital Signature Algorithm (ECDSA).

The following code example explains how to add a digital signature to the PDF document.

C#

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

PdfCertificate pdfCert = new PdfCertificate(@"PDF.pfx", "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

PdfBitmap signatureImage = new PdfBitmap(@"signature.jpg");

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Saves and closes the document

document.Save("Output.pdf");

document.Close(true);

VB.NET

'Creates a new PDF document

Dim document As New PdfDocument()

'Adds a new page

Dim page As PdfPageBase = document.Pages.Add()

Dim graphics As PdfGraphics = page.Graphics

'Creates a certificate instance from PFX file with private key

Dim pdfCert As New PdfCertificate("PDF.pfx", "password123")

'Creates a digital signature

Dim signature As New PdfSignature(document, page, pdfCert, "Signature")

'Sets an image for signature field

Dim signatureImage As New PdfBitmap("signature.jpg")

'Sets signature info

signature.Bounds = New RectangleF(New PointF(0, 0), signatureImage.PhysicalDimension)

signature.ContactInfo = "[e-mail]"

signature.LocationInfo = "Honolulu, Hawaii"

signature.Reason = "I am author of this document."

'Draws the signature image

graphics.DrawImage(signatureImage, 0, 0)

'Saves and closes the document

document.Save("Output.pdf")

document.Close(True)

UWP

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.signature.jpg");

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

await document.SaveAsync(stream);

//Close the document

document.Close(true);                                                                   

//Save the stream as PDF document file in local machine. Refer to the PDF/UWP section for respective code samples

Save(stream, "Output.pdf");

ASP.NET Core

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

FileStream certificateStream = new FileStream("PDF.pfx", FileMode.Open, FileAccess.Read);

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

FileStream imageStream = new FileStream("signature.jpg", FileMode.Open, FileAccess.Read);

//Sets an image for signature field

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the document into stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

stream.Position = 0;

//Close the documents

document.Close(true);

//Defining the ContentType for pdf file

string contentType = "application/pdf";

//Define the file name

string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name

return File(stream, contentType, fileName);

Xamarin

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.signature.jpg");

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

//Closes the document

document.Close(true);

//Save the stream into PDF file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)
{
    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", stream);
}
else
{
    Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", stream);
}

Adding a digital signature using stream

The following code example illustrates how to add a digital signature in the PDF document
using stream as follows.

C#

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Gets a stream from .pfx file

Stream pfxStream = File.OpenRead("PDF.pfx");

//Creates a certificate instance from PFX file stream with private key

PdfCertificate pdfCert = new PdfCertificate(pfxStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

PdfBitmap signatureImage = new PdfBitmap(@"signature.jpg");

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Saves and closes the document

document.Save("Output.pdf");

document.Close(true);

VB.NET

'Creates a new PDF document

Dim document As New PdfDocument()

'Adds a new page

Dim page As PdfPageBase = document.Pages.Add()

Dim graphics As PdfGraphics = page.Graphics

'Gets stream from .pfx file

Dim pfxStream As Stream = File.OpenRead("PDF.pfx")

'Creates a certificate instance from PFX file stream with private key

Dim pdfCert As New PdfCertificate(pfxStream, "password123")

'Creates a digital signature

Dim signature As New PdfSignature(document, page, pdfCert, "Signature")

'Sets an image for signature field

Dim signatureImage As New PdfBitmap("signature.jpg")

'Sets signature information

signature.Bounds = New RectangleF(New PointF(0, 0), signatureImage.PhysicalDimension)

signature.ContactInfo = "[e-mail]"

signature.LocationInfo = "Honolulu, Hawaii"

signature.Reason = "I am author of this document."

'Draws the signature image

graphics.DrawImage(signatureImage, 0, 0)

'Saves and closes the document

document.Save("Output.pdf")

document.Close(True)

UWP

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.signature.jpg");

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

await document.SaveAsync(stream);

//Close the document

document.Close(true);                                                                   

//Save the stream as PDF document file in local machine. Refer to the PDF/UWP section for respective code samples

Save(stream, "output.pdf");

ASP.NET Core

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

FileStream certificateStream = new FileStream("PDF.pfx", FileMode.Open, FileAccess.Read);

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

FileStream imageStream = new FileStream("signature.jpg", FileMode.Open, FileAccess.Read);

//Sets an image for signature field

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the document into stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

stream.Position = 0;

//Close the documents

document.Close(true);

//Defining the ContentType for pdf file

string contentType = "application/pdf";

//Define the file name

string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name

return File(stream, contentType, fileName);

Xamarin

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.signature.jpg");

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

//Closes the document

document.Close(true);

//Save the stream into PDF file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)
{
    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("sample.pdf", "application/pdf", stream);
}
else
{
    Xamarin.Forms.DependencyService.Get<ISave>().Save("sample.pdf", "application/pdf", stream);
}

You can add a digital signature to an existing document as follows.

C#

//Loads the PDF document with signature field

PdfLoadedDocument loadedDocument = new PdfLoadedDocument("Input.pdf");         

//Gets the page

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Creates a signature field

PdfSignatureField signatureField = new PdfSignatureField(page, "SignatureField");

signatureField.Bounds = new RectangleF(0, 0, 100, 100);

signatureField.Signature = new PdfSignature();

//Adds certificate to the signature field

signatureField.Signature.Certificate = new PdfCertificate(@"PDF.pfx", "password123");

signatureField.Signature.Reason = "I am author of this document";

//Adds the field

loadedDocument.Form.Fields.Add(signatureField);

//Saves the certified PDF document

loadedDocument.Save(@"Output.pdf");

loadedDocument.Close(true);

VB.NET

'Loads the PDF document with signature field

Dim loadedDocument As New PdfLoadedDocument("Input.pdf")

'Gets the page

Dim page As PdfLoadedPage = TryCast(loadedDocument.Pages(0), PdfLoadedPage)

'Creates a signature field

Dim signatureField As New PdfSignatureField(page, "SignatureField")

signatureField.Bounds = New RectangleF(0, 0, 100, 100)

signatureField.Signature = New PdfSignature()

'Adds certificate to the signature field

signatureField.Signature.Certificate = New PdfCertificate("PDF.pfx", "password123")

signatureField.Signature.Reason = "I am author of this document"

'Adds the field

loadedDocument.Form.Fields.Add(signatureField)

'Saves the certified PDF document

loadedDocument.Save("Output.pdf")

loadedDocument.Close(True)

UWP

//Create the file open picker

var picker = new FileOpenPicker();

picker.FileTypeFilter.Add(".pdf");

//Browse and chose the file

StorageFile file = await picker.PickSingleFileAsync();

//Creates an empty PDF loaded document instance

PdfLoadedDocument loadedDocument = new PdfLoadedDocument();

//Loads or opens an existing PDF document through Open method of PdfLoadedDocument class

await loadedDocument.OpenAsync(file);

//Gets the page

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Creates a signature field

PdfSignatureField signatureField = new PdfSignatureField(page, "SignatureField");

signatureField.Bounds = new RectangleF(0, 0, 100, 100);

signatureField.Signature = new PdfSignature();

//Adds certificate to the signature field

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.

signatureField.Signature.Certificate = new PdfCertificate(certificateStream, "password123");

signatureField.Signature.Reason = "I am author of this document";

//Adds the field

loadedDocument.Form.Fields.Add(signatureField);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

await loadedDocument.SaveAsync(stream);

//Close the document

loadedDocument.Close(true);                                                                   

//Save the stream as PDF document file in local machine. Refer to the PDF/UWP section for respective code samples

Save(stream, "Output.pdf");

ASP.NET Core

//Load the PDF document

FileStream docStream = new FileStream("Input.pdf", FileMode.Open, FileAccess.Read);

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(docStream);

//Gets the page

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Creates a signature field

PdfSignatureField signatureField = new PdfSignatureField(page, "SignatureField");

signatureField.Bounds = new RectangleF(0, 0, 100, 100);

signatureField.Signature = new PdfSignature();

//Adds certificate to the signature field

FileStream certificateStream = new FileStream("PDF.pfx", FileMode.Open, FileAccess.Read);

signatureField.Signature.Certificate = new PdfCertificate(certificateStream, "password123");

signatureField.Signature.Reason = "I am author of this document";

//Adds the field

loadedDocument.Form.Fields.Add(signatureField);

//Save the document into stream

MemoryStream stream = new MemoryStream();

loadedDocument.Save(stream);

stream.Position = 0;

//Close the documents

loadedDocument.Close(true);

//Defining the ContentType for pdf file

string contentType = "application/pdf";

//Define the file name

string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name

return File(stream, contentType, fileName);

Xamarin

//Load the file as stream

Stream docStream = typeof(App).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Input.pdf");

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(docStream);

//Gets the page

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Creates a signature field

PdfSignatureField signatureField = new PdfSignatureField(page, "SignatureField");

signatureField.Bounds = new RectangleF(0, 0, 100, 100);

signatureField.Signature = new PdfSignature();

//Adds certificate to the signature field

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF.pfx");

signatureField.Signature.Certificate = new PdfCertificate(certificateStream, "password123");

signatureField.Signature.Reason = "I am author of this document";

//Adds the field

loadedDocument.Form.Fields.Add(signatureField);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

loadedDocument.Save(stream);

//Closes the document

loadedDocument.Close(true);

//Save the stream into PDF file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)
{
    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", stream);
}
else
{
    Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", stream);
}

Adding a digital signature using X509Certificate2

The following code example illustrates how to add digital signature in a PDF document using X509Certificate2 as follows.

C#

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page  

PdfPage page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key  

X509Certificate2 certificate = new X509Certificate2("PDF.pfx", "password123");

PdfCertificate pdfCertificate = new PdfCertificate(certificate);

//Creates a digital signature  

PdfSignature signature = new PdfSignature(document, page, pdfCertificate, "Signature");

//Sets an image for signature field

PdfBitmap signatureImage = new PdfBitmap(@"signature.jpg");

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the document

document.Save("Output.pdf");

//Close the document

document.Close(true);

VB.NET

'Creates a new PDF document

Dim document As New PdfDocument()

'Adds a new page  

Dim page As PdfPage = document.Pages.Add()

Dim graphics As PdfGraphics = page.Graphics

'Creates a certificate instance from PFX file with private key  

Dim certificate As New X509Certificate2("PDF.pfx", "password123")

Dim pdfCertificate As New PdfCertificate(certificate)

'Creates a digital signature 

Dim signature As New PdfSignature(document, page, pdfCertificate, "Signature")

'Sets an image for signature field

Dim signatureImage As New PdfBitmap("signature.jpg")

'Sets signature information

signature.Bounds = New RectangleF(New PointF(0, 0), signatureImage.PhysicalDimension)

signature.ContactInfo = "[e-mail]"

signature.LocationInfo = "Honolulu, Hawaii"

signature.Reason = "I am author of this document."

'Draws the signature image

graphics.DrawImage(signatureImage, 0, 0)

'Save the document

document.Save("Output.pdf")

'Close the document

document.Close(True)

UWP

//Essential PDF supports adding a digital signature using X509Certificate2 only in Windows Forms, WPF, ASP.NET, ASP.NET MVC, and ASP.NET Core platforms.

ASP.NET Core

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page  

PdfPage page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key  

X509Certificate2 certificate = new X509Certificate2("PDF.pfx", "password123");

PdfCertificate pdfCertificate = new PdfCertificate(certificate);

//Creates a digital signature  

PdfSignature signature = new PdfSignature(document, page, pdfCertificate, "Signature");

//Sets an image for signature field

FileStream imageStream = new FileStream("signature.jpg", FileMode.Open, FileAccess.Read);

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Creating the stream object

MemoryStream stream = new MemoryStream();

//Save the document as stream

document.Save(stream);

//If the position is not set to '0', then the PDF will be empty

stream.Position = 0;

//Close the document

document.Close(true);

//Defining the ContentType for pdf file

string contentType = "application/pdf";

//Define the file name

string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name

return File(stream, contentType, fileName);

Xamarin

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page  

PdfPage page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key  

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF.pfx");

MemoryStream ms = new MemoryStream();

certificateStream.CopyTo(ms);

X509Certificate2 certificate = new X509Certificate2(ms.ToArray(), "password123");

PdfCertificate pdfCertificate = new PdfCertificate(certificate);

//Creates a digital signature  

PdfSignature signature = new PdfSignature(document, page, pdfCertificate, "Signature");

//Sets an image for signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.signature.jpg");

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the document as stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

//Close the document

document.Close(true);

//Save the stream into PDF file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples

if (Device.RuntimePlatform == Device.UWP)
{
    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", stream);
}
else
{
    Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", stream);
}

Signing an existing document

You can load the signature field from the existing PDF document and add certificate to the document as follows.

C#

//Loads a PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument("Input.pdf");

//Gets the first page of the document

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Gets the first signature field of the PDF document

PdfLoadedSignatureField field = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

//Creates a certificate

PdfCertificate certificate = new PdfCertificate(@"PDF.pfx", "password123");

field.Signature = new PdfSignature(loadedDocument,page,certificate,"Signature",field);

//Saves the document

loadedDocument.Save("Output.pdf");

//Closes the document

loadedDocument.Close(true);

VB.NET

'Loads a PDF document

Dim loadedDocument As New PdfLoadedDocument("Input.pdf")

'Gets the first page of the document

Dim page As PdfLoadedPage = TryCast(loadedDocument.Pages(0), PdfLoadedPage)

'Gets the first signature field of the PDF document

Dim field As PdfLoadedSignatureField = TryCast(loadedDocument.Form.Fields(0), PdfLoadedSignatureField)

'Creates a certificate

Dim certificate As New PdfCertificate("PDF.pfx", "password123")

field.Signature = New PdfSignature(loadedDocument, page, certificate, "Signature", field)

'Saves the document

loadedDocument.Save("Output.pdf")

'Closes the document

loadedDocument.Close(True)

UWP

//Create the file open picker

var picker = new FileOpenPicker();

picker.FileTypeFilter.Add(".pdf");

//Browse and chose the file

StorageFile file = await picker.PickSingleFileAsync();

//Creates an empty PDF loaded document instance

PdfLoadedDocument loadedDocument = new PdfLoadedDocument();

//Loads or opens an existing PDF document through Open method of PdfLoadedDocument class

await loadedDocument.OpenAsync(file);

//Gets the first page of the document

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Gets the first signature field of the PDF document

PdfLoadedSignatureField field = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

//Creates a certificate

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.

PdfCertificate certificate = new PdfCertificate(certificateStream, "password123");

field.Signature = new PdfSignature(loadedDocument, page, certificate, "Signature", field);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

await loadedDocument.SaveAsync(stream);

//Close the document

loadedDocument.Close(true);                                                                   

//Save the stream as PDF document file in local machine. Refer to PDF/UWP section for respected code samples

Save(stream, "Output.pdf");

ASP.NET Core

//Load the PDF document

FileStream docStream = new FileStream("Input.pdf", FileMode.Open, FileAccess.Read);

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(docStream);

//Gets the first page of the document

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Gets the first signature field of the PDF document

PdfLoadedSignatureField field = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

//Creates a certificate

FileStream certificateStream = new FileStream("PDF.pfx", FileMode.Open, FileAccess.Read);

PdfCertificate certificate = new PdfCertificate(certificateStream, "password123");

field.Signature = new PdfSignature(loadedDocument, page, certificate, "Signature", field);

//Save the document into stream

MemoryStream stream = new MemoryStream();

loadedDocument.Save(stream);

stream.Position = 0;

//Close the documents

loadedDocument.Close(true);

//Defining the ContentType for pdf file

string contentType = "application/pdf";

//Define the file name

string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name

return File(stream, contentType, fileName);

Xamarin

//Load the file as stream

Stream docStream = typeof(App).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Sample.pdf");

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(docStream);

//Gets the first page of the document

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Gets the first signature field of the PDF document

PdfLoadedSignatureField field = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

//Creates a certificate

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF.pfx");

PdfCertificate certificate = new PdfCertificate(certificateStream, "password123");

field.Signature = new PdfSignature(loadedDocument, page, certificate, "Signature", field);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

loadedDocument.Save(stream);

//Closes the document

loadedDocument.Close(true);

//Save the stream into PDF file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)
{
    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", stream);
}
else
{
    Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", stream);
}

Sign an existing document using stream

You can load the signature field from an existing PDF document and add certificate to the document using stream as follows.

C#

//Loads a PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument("Input.pdf");

//Gets the first page of the document

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Gets the first signature field of the PDF document

PdfLoadedSignatureField field = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

//Gets the stream from .pfx file

Stream pfxStream = File.OpenRead("PDF.pfx");

//Creates a certificate instance from PFX file stream with private key

PdfCertificate certificate = new PdfCertificate(pfxStream, "password123");

field.Signature = new PdfSignature(loadedDocument, page, certificate, "Signature", field);

//Saves the document

loadedDocument.Save("Output.pdf");

//Closes the document

loadedDocument.Close(true);

VB.NET

'Loads a PDF document

Dim loadedDocument As New PdfLoadedDocument("Input.pdf")

'Gets the first page of the document

Dim page As PdfLoadedPage = TryCast(loadedDocument.Pages(0), PdfLoadedPage)

'Gets the first signature field of the PDF document

Dim field As PdfLoadedSignatureField = TryCast(loadedDocument.Form.Fields(0), PdfLoadedSignatureField)

'Gets the stream from .pfx file

Dim pfxStream As Stream = File.OpenRead("PDF.pfx")

'Creates a certificate instance from PFX file stream with private key

Dim certificate As New PdfCertificate(pfxStream, "password123")

field.Signature = New PdfSignature(loadedDocument, page, certificate, "Signature", field)

'Saves the document

loadedDocument.Save("Output.pdf")

'Closes the document

loadedDocument.Close(True)

UWP

//Create the file open picker

var picker = new FileOpenPicker();

picker.FileTypeFilter.Add(".pdf");

//Browse and chose the file

StorageFile file = await picker.PickSingleFileAsync();

//Creates an empty PDF loaded document instance

PdfLoadedDocument loadedDocument = new PdfLoadedDocument();

//Loads or opens an existing PDF document through Open method of PdfLoadedDocument class

await loadedDocument.OpenAsync(file);

//Gets the first page of the document

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Gets the first signature field of the PDF document

PdfLoadedSignatureField field = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

//Creates a certificate

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.PDF.pfx");

PdfCertificate certificate = new PdfCertificate(certificateStream, "password123");

field.Signature = new PdfSignature(loadedDocument, page, certificate, "Signature", field);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

await loadedDocument.SaveAsync(stream);

//Close the document

loadedDocument.Close(true);                                                                   

//Save the stream as PDF document file in local machine. Refer to PDF/UWP section for respected code samples

Save(stream, "output.pdf");

ASP.NET Core

//Load the PDF document

FileStream docStream = new FileStream("Input.pdf", FileMode.Open, FileAccess.Read);

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(docStream);

//Gets the first page of the document

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Gets the first signature field of the PDF document

PdfLoadedSignatureField field = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

//Creates a certificate

FileStream certificateStream = new FileStream("PDF.pfx", FileMode.Open, FileAccess.Read);

PdfCertificate certificate = new PdfCertificate(certificateStream, "password123");

field.Signature = new PdfSignature(loadedDocument, page, certificate, "Signature", field);

//Save the document into stream

MemoryStream stream = new MemoryStream();

loadedDocument.Save(stream);

stream.Position = 0;

//Close the documents

loadedDocument.Close(true);

//Defining the ContentType for pdf file

string contentType = "application/pdf";

//Define the file name

string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name

return File(stream, contentType, fileName);

Xamarin

//Load the file as stream

Stream docStream = typeof(App).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Sample.pdf");

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(docStream);

//Gets the first page of the document

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Gets the first signature field of the PDF document

PdfLoadedSignatureField field = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

//Creates a certificate

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF.pfx");

PdfCertificate certificate = new PdfCertificate(certificateStream, "password123");

field.Signature = new PdfSignature(loadedDocument, page, certificate, "Signature", field);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

loadedDocument.Save(stream);

//Closes the document

loadedDocument.Close(true);

//Save the stream into PDF file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)
{
    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", stream);
}
else
{
    Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", stream);
}

Externally sign a PDF document

You can sign the PDF document from external digital signature created from various sources such as HSM, USB token, smart card, or other cloud services such as DigitalSign.

The following code example shows how to sign the PDF document from external signature.

C#

//Load existing PDF document

PdfLoadedDocument document = new PdfLoadedDocument("PDF_Succinctly.pdf");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, document.Pages[0], null, "DigitalSignature");

signature.ComputeHash += Signature_ComputeHash;

//Save the PDF document

document.Save("ExternalSignature.pdf");

//Close the document

document.Close(true);

void Signature_ComputeHash(object sender, PdfSignatureEventArgs arguments)

{

//Get the document bytes

byte[] documentBytes = arguments.Data;

SignedCms signedCms = new SignedCms(new ContentInfo(documentBytes), detached: true);

//Compute the signature using the specified digital ID file and the password

X509Certificate2 certificate = new X509Certificate2("DigitalSignatureTest.pfx", "DigitalPass123");

var cmsSigner = new CmsSigner(certificate);

//Set the digest algorithm SHA256

cmsSigner.DigestAlgorithm = new Oid("2.16.840.1.101.3.4.2.1");


signedCms.ComputeSignature(cmsSigner);

//Embed the encoded digital signature to the PDF document

arguments.SignedData = signedCms.Encode();

}

VB.NET

'Load existing PDF document

Dim document As PdfLoadedDocument = New PdfLoadedDocument("PDF_Succinctly.pdf")

'Creates a digital signature

Dim signature As PdfSignature = New PdfSignature(document, document.Pages(0), Nothing, "DigitalSignature")

signature.ComputeHash += Signature_ComputeHash

'Save the PDF document

document.Save("ExternalSignature.pdf")

'Close the document

document.Close(True)

Private Sub Signature_ComputeHash(ByVal sender As Object, ByVal arguments As PdfSignatureEventArgs)

'Get the document bytes

Dim documentBytes As Byte() = arguments.Data

Dim signedCms As SignedCms = New SignedCms(New ContentInfo(documentBytes), detached:=True)

'Compute the signature using the specified digital ID file and the password

Dim certificate As X509Certificate2 = New X509Certificate2("DigitalSignatureTest.pfx", "DigitalPass123")

Dim cmsSigner = New CmsSigner(certificate)

'Set the digest algorithm SHA256

cmsSigner.DigestAlgorithm = New Oid("2.16.840.1.101.3.4.2.1")

signedCms.ComputeSignature(cmsSigner)

'Embed the encoded digital signature to the PDF document

arguments.SignedData = signedCms.Encode()

End Sub

UWP

//Get the stream from the document

Stream documentStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data. PDF_Succinctly.pdf");

//Load an existing signed PDF document

PdfLoadedDocument document = new PdfLoadedDocument(documentStream);

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, document.Pages[0], null, "DigitalSignature");

signature.ComputeHash += Signature_ComputeHash;

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

await document.SaveAsync(stream);

//Close the document

document.Close(true);

//Save the stream as PDF document file in local machine. Refer to the PDF/UWP section for respective code samples

Save(stream, " ExternalSignature.pdf");

private static void Signature_ComputeHash1(object sender, PdfSignatureEventArgs ars)

{

//Get the document bytes

byte[] documentBytes = ars.Data;

SignedCms signedCms = new SignedCms(new ContentInfo(documentBytes), detached: true);

//Compute the signature using the specified digital ID file and the password

X509Certificate2 certificate = new X509Certificate2("DigitalSignatureTest.pfx", "DigitalPass123");

var cmsSigner = new CmsSigner(certificate);

//Set the digest algorithm SHA256

cmsSigner.DigestAlgorithm = new Oid("2.16.840.1.101.3.4.2.1");

signedCms.ComputeSignature(cmsSigner);

//Embed the encoded digital signature to the PDF document

ars.SignedData = signedCms.Encode();

}

ASP.NET Core

//Get the stream from the document

FileStream documentStream = new FileStream("PDF_Succinctly.pdf ", FileMode.Open, FileAccess.Read);

//Load the existing PDF document

PdfLoadedDocument document = new PdfLoadedDocument(documentStream);

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, document.Pages[0], null, "DigitalSignature");

signature.ComputeHash += Signature_ComputeHash;

MemoryStream ms = new MemoryStream();

document.Save(ms);

document.Close(true);

private static void Signature_ComputeHash1(object sender, PdfSignatureEventArgs ars)
{
//Get the document bytes

byte[] documentBytes = ars.Data;

SignedCms signedCms = new SignedCms(new ContentInfo(documentBytes), detached: true);

//Compute the signature using the specified digital ID file and the password

X509Certificate2 certificate = new X509Certificate2("DigitalSignatureTest.pfx", "DigitalPass123");

var cmsSigner = new CmsSigner(certificate);

//Set the digest algorithm SHA256

cmsSigner.DigestAlgorithm = new Oid("2.16.840.1.101.3.4.2.1");

signedCms.ComputeSignature(cmsSigner);

//Embed the encoded digital signature to the PDF document

ars.SignedData = signedCms.Encode();

}

Xamarin

//Get the stream from the document

Stream documentStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF_Succinctly.pdf");

//Load an existing signed PDF document

PdfLoadedDocument document = new PdfLoadedDocument(documentStream);

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, document.Pages[0], null, "DigitalSignature");

signature.ComputeHash += Signature_ComputeHash;

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

//Closes the document

document.Close(true);

//Save the stream into pdf file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)

{

Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("ExternalSignature.pdf", "application/pdf", stream);

}

else

{

Xamarin.Forms.DependencyService.Get<ISave>().Save("ExternalSignature.pdf", "application/pdf", stream);

}

private static void Signature_ComputeHash1(object sender, PdfSignatureEventArgs ars)

{

//Get the document bytes

byte[] documentBytes = ars.Data;

SignedCms signedCms = new SignedCms(new ContentInfo(documentBytes), detached: true);

//Compute the signature using the specified digital ID file and the password

X509Certificate2 certificate = new X509Certificate2("DigitalSignatureTest.pfx", "DigitalPass123");

var cmsSigner = new CmsSigner(certificate);

//Set the digest algorithm SHA256

cmsSigner.DigestAlgorithm = new Oid("2.16.840.1.101.3.4.2.1");

signedCms.ComputeSignature(cmsSigner);

//Embed the encoded digital signature to the PDF document

ars.SignedData = signedCms.Encode();

}

Create Long Term Validation (LTV) when signing PDF documents externally

You can create a Long Term validation (LTV) when signing PDF documents externally using your private/public certificates.

The following code example shows how to create an LTV when signing a PDF document from external signature.

C#

//Load an existing PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument("Input.pdf");

//Get the page of the existing PDF document

PdfLoadedPage loadedPage = loadedDocument.Pages[0] as PdfLoadedPage;

//Create a new PDF signature without PdfCertificate instance

PdfSignature signature = new PdfSignature(loadedDocument, loadedPage, null, "Signature1");

//Hook up the ComputeHash event

signature.ComputeHash += Signature_ComputeHash;

//Create X509Certificate2 from your certificate to create a long-term validity

X509Certificate2 x509 = new X509Certificate2("PDF.pfx", "password123");

//Create LTV with your public certificates

signature.CreateLongTermValidity(new List<X509Certificate2> { x509 });

//Save and close the PDF document

loadedDocument.Save("SignedDocument.pdf");

loadedDocument.Close(true);

VB.NET

'Load an existing PDF document

Dim loadedDocument As PdfLoadedDocument = New PdfLoadedDocument("Input.pdf")

'Get the page of the existing PDF document

Dim loadedPage As PdfLoadedPage = TryCast(loadedDocument.Pages(0), PdfLoadedPage)

'Create a new PDF signature without PdfCertificate instance

Dim signature As PdfSignature = New PdfSignature(loadedDocument, loadedPage, Nothing, "Signature1")

' Hook up the ComputeHash event

AddHandler signature.ComputeHash, AddressOf Signature_ComputeHash

'Create X509Certificate2 from your certificate to create a long-term validity

Dim x509 As X509Certificate2 = New X509Certificate2("PDF.pfx", "password123")

'Create LTV with your public certificates

signature.CreateLongTermValidity(New List(Of X509Certificate2) From { x509 })

'Save and close the PDF document

loadedDocument.Save("SignedDocument.pdf")

loadedDocument.Close(True)

UWP

//Get the stream from the document

Stream documentStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Input.pdf");

//Load an existing PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//Get the page of the existing PDF document

PdfLoadedPage loadedPage = loadedDocument.Pages[0] as PdfLoadedPage;

//Create a new PDF signature without PdfCertificate instance

PdfSignature signature = new PdfSignature(loadedDocument, loadedPage, null, "Signature1");

//Hook up the ComputeHash event

signature.ComputeHash += Signature_ComputeHash;

//Create X509Certificate2 from your certificate to create a long-term validity

X509Certificate2 x509 = new X509Certificate2("PDF.pfx", "password123");

//Create LTV with your public certificates

signature.CreateLongTermValidity(new List<X509Certificate2> { x509 });

//Save the PDF document

MemoryStream stream = new MemoryStream();

loadedDocument.Save(stream);

stream.Position = 0;

//Save the stream as PDF document file in local machine. Refer to the PDF/UWP section for respective code samples

Save(stream, "Output.pdf");

ASP.NET Core

//Get the stream from the document

FileStream documentStream = new FileStream("Input.pdf ", FileMode.Open, FileAccess.Read);

//Load an existing PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//Get the page of the existing PDF document

PdfLoadedPage loadedPage = loadedDocument.Pages[0] as PdfLoadedPage;

//Create a new PDF signature without PdfCertificate instance

PdfSignature signature = new PdfSignature(loadedDocument, loadedPage, null, "Signature1");

//Hook up the ComputeHash event

signature.ComputeHash += Signature_ComputeHash;

//Create X509Certificate2 from your certificate to create a long-term validity

X509Certificate2 x509 = new X509Certificate2("PDF.pfx", "password123");

//Create LTV with your public certificates

signature.CreateLongTermValidity(new List<X509Certificate2> { x509 });

//Save the PDF document

MemoryStream stream = new MemoryStream();

loadedDocument.Save(stream);

stream.Position = 0;

//Close the document

loadedDocument.Close(true);

//Defining the ContentType for pdf file

string contentType = "application/pdf";

//Define the file name

string fileName = "Output.pdf";

//Creates a File object by using the file contents, content type, and file name

return File(stream, contentType, fileName);

Xamarin

//Get the stream from the document

Stream documentStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets. Input.pdf");

//Load an existing PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//Get the page of the existing PDF document

PdfLoadedPage loadedPage = loadedDocument.Pages[0] as PdfLoadedPage;

//Create a new PDF signature without PdfCertificate instance

PdfSignature signature = new PdfSignature(loadedDocument, loadedPage, null, "Signature1");

//Hook up the ComputeHash event

signature.ComputeHash += Signature_ComputeHash;

//Create X509Certificate2 from your certificate to create a long-term validity

X509Certificate2 x509 = new X509Certificate2("PDF.pfx", "password123");

//Create LTV with your public certificates

signature.CreateLongTermValidity(new List<X509Certificate2> { x509 });

//Save the PDF document

MemoryStream stream = new MemoryStream();

loadedDocument.Save(stream);

stream.Position = 0;

//Save the stream into pdf file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)
{
    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", stream);
}
else
{
    Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", stream);
}

Adding a signature validation appearance based on the signature

You can add the dynamic signature validation appearance to the signature field by enabling the EnableValidationAppearance property available in the PdfSignature class, the appearance will change based on the PDF reader validation.

Refer to the following code sample.

C#

//Creates a new PDF document

PdfDocument document = new PdfDocument();
         
//Add a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics=page.Graphics;

//Creates a certificate instance from the PFX file with private key
            
PdfCertificate pdfCert = new PdfCertificate(@"PDF.pfx", "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for the signature field

PdfBitmap signatureImage = new PdfBitmap(@"signature.jpg");

//Sets enable signature validation appearance

signature.EnableValidationAppearance = true;

//Sets signature information

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draw the signature image
      
graphics.DrawImage(signatureImage, 0, 0);
 
//Save and close documents

document.Save("Output.pdf");

document.Close( true );

VB.NET

'Creates a new PDF document

Dim document As New PdfDocument()

'Adds a new page

Dim page As PdfPageBase = document.Pages.Add()

Dim graphics As PdfGraphics = page.Graphics

'Creates a certificate instance from the PFX file with private key

Dim pdfCert As New PdfCertificate("PDF.pfx", "password123")

'Creates a digital signature

Dim signature As New PdfSignature(document, page, pdfCert, "Signature")

'Sets an image for the signature field

Dim signatureImage As New PdfBitmap("signature.jpg")

‘Sets enable signature validation appearance
        
signature.EnableValidationAppearance = True

'Sets signature info

signature.Bounds = New RectangleF(New PointF(0, 0), signatureImage.PhysicalDimension)

signature.ContactInfo = "[e-mail]"

signature.LocationInfo = "Honolulu, Hawaii"

signature.Reason = "I am author of this document."

'Draws the signature image

graphics.DrawImage(signatureImage, 0, 0)

'Saves and closes the document

document.Save("Output.pdf")

document.Close(True)

UWP

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from the PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.signature.jpg");

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets enable signature validation appearance

signature.EnableValidationAppearance = true;

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

await document.SaveAsync(stream);

//Close the document

document.Close(true);

//Save the stream as PDF document file in local machine. Refer to the PDF/UWP section for respective code samples

Save(stream, "Output.pdf");

ASP.NET Core

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from the PFX file with private key

FileStream certificateStream = new FileStream("PDF.pfx", FileMode.Open, FileAccess.Read);

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for the signature field

FileStream imageStream = new FileStream("signature.jpg", FileMode.Open, FileAccess.Read);

//Sets an image for signature field

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets enable signature validation appearance

signature.EnableValidationAppearance = true;

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the document into stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

stream.Position = 0;

//Close the documents

document.Close(true);

//Defining the ContentType for PDF file

string contentType = "application/pdf";

//Define the file name

string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name

return File(stream, contentType, fileName);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

await document.SaveAsync(stream);

//Close the document

document.Close(true);

//Save the stream as PDF document file in local machine. Refer to the PDF/UWP section for respective code samples

Save(stream, "Output.pdf");

Xamarin

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from the PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for the signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.signature.jpg");

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets enable signature validation appearance

signature.EnableValidationAppearance = true;

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

//Closes the document

document.Close(true);

//Save the stream into PDF file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples.

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)
         
{

Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", stream);
           
}

else

{

Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", stream);

}

Adding a timestamp in digital signature

Essential PDF allows you to add timestamp in the digital signature of the PDF document. The following code example explains the same.

C#

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPage page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

PdfCertificate pdfCert = new PdfCertificate(@"PDF.pfx", "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(page, pdfCert, "Signature");

//Sets an image for signature field

PdfBitmap image = new PdfBitmap(@"syncfusion_logo.jpeg");

//Adds time stamp by using the server URI and credentials

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

//Sets signature info

signature.Bounds = new RectangleF(new PointF(0, 0), image.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(image, 0, 0);

//Saves and closes the document

document.Save("Output.pdf");

document.Close(true);

VB.NET

'Creates a new PDF document

Dim document As New PdfDocument()

'Adds a new page

Dim page As PdfPage = document.Pages.Add()

Dim graphics As PdfGraphics = page.Graphics

'Creates a certificate instance from PFX file with private key

Dim pdfCert As New PdfCertificate("PDF.pfx", "password123")

'Creates a digital signature

Dim signature As New PdfSignature(page, pdfCert, "Signature")

'Sets an image for signature field

Dim image As New PdfBitmap("syncfusion_logo.jpeg")

'Adds time stamp by using the server URI and credentials

signature.TimeStampServer = New TimeStampServer(New Uri("http://syncfusion.digistamp.com"), "user", "123456")

'Sets signature info

signature.Bounds = New RectangleF(New PointF(0, 0), image.PhysicalDimension)

signature.ContactInfo = "[e-mail]"

signature.LocationInfo = "Honolulu, Hawaii"

signature.Reason = "I am author of this document."

'Draws the signature image

graphics.DrawImage(image, 0, 0)

'Saves and closes the document

document.Save("Output.pdf")

document.Close(True)

UWP

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.syncfusion_logo.jpeg");

PdfBitmap image = new PdfBitmap(imageStream);

//Adds time stamp by using the server URI and credentials

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

//Sets signature info

signature.Bounds = new RectangleF(new PointF(0, 0), image.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(image, 0, 0);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

await document.SaveAsync(stream);

//Close the document

document.Close(true);

//Save the stream as PDF document file in local machine. Refer to the PDF/UWP section for respective code samples

Save(stream, "output.pdf");

ASP.NET Core

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

FileStream certificateStream = new FileStream("PDF.pfx", FileMode.Open, FileAccess.Read);

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

FileStream imageStream = new FileStream("syncfusion_logo.jpeg", FileMode.Open, FileAccess.Read);

//Sets an image for signature field

PdfBitmap image = new PdfBitmap(imageStream);

//Adds time stamp by using the server URI and credentials

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

//Sets signature info

signature.Bounds = new RectangleF(new PointF(0, 0), image.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(image, 0, 0);

//Save the document into stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

stream.Position = 0;

//Close the documents

document.Close(true);

//Defining the ContentType for pdf file

string contentType = "application/pdf";

//Define the file name

string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name

return File(stream, contentType, fileName);

Xamarin

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.syncfusion_logo.jpeg");

PdfBitmap image = new PdfBitmap(imageStream);

//Adds time stamp by using the server URI and credentials

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

//Sets signature info

signature.Bounds = new RectangleF(new PointF(0, 0), image.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(image, 0, 0);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

//Closes the document

document.Close(true);

//Save the stream into PDF file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)
{
    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("sample.pdf", "application/pdf", stream);
}
else
{
    Xamarin.Forms.DependencyService.Get<ISave>().Save("sample.pdf", "application/pdf", stream);
}

Adding a timestamp to PDF document

You can add timestamp to the PDF document using the following code snippet.

C#

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPage page = document.Pages.Add();

//Creates a digital signature

PdfSignature signature = new PdfSignature(page, "Signature");

//Add the time stamp by using the server URI

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

//Save and close the document

document.Save("Output.pdf");

document.Close(true);

VB.NET

'Creates a new PDF document

Dim document As New PdfDocument()

'Adds a new page

Dim page As PdfPage = document.Pages.Add()

'Creates a digital signature

Dim signature As New PdfSignature(page, "Signature")

'Adds time stamp by using the server URI

signature.TimeStampServer = New TimeStampServer(New Uri("http://syncfusion.digistamp.com"), "user", "123456")

'Saves and closes the document

document.Save("Output.pdf")

document.Close(True)

UWP

//Create a new document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPage page = document.Pages.Add();        

//Creates a digital signature

PdfSignature signature = new PdfSignature(page, "Signature");

//Add the time stamp by using the server URI

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

await document.SaveAsync(stream);

//Close the document

document.Close(true);

//Save the stream as PDF document file in local machine. Refer to PDF/UWP section for respected code samples. 

Save(stream, "Output.pdf");

ASP.NET Core

//Create a new pdf document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPage page = document.Pages.Add();

//Creates a digital signature

PdfSignature signature = new PdfSignature(page, "Signature");

//Add the time stamp by using the server URI

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

//Save the document into stream

MemoryStream stream = new MemoryStream();

loadedDocument.Save(stream);

stream.Position = 0;

//Close the document
 
loadedDocument.Close(true);

//Defining the ContentType for pdf file

string contentType = "application/pdf";

//Define the file name

string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name

return File(stream, contentType, fileName);

Xamarin

//Create a new PDF document

PdfDocument document = new PdfDocument();            

//Add a page

PdfPage page = document.Pages.Add();

//Creates a digital signature

PdfSignature signature = new PdfSignature(page, "Signature");

//Add the time stamp by using the server URI

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

//Save the document into stream

MemoryStream memoryStream = new MemoryStream();

document.Save(memoryStream);

//Save the stream into PDF file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples.

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)

{

        Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", memoryStream);

}

else

{
 

       Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", memoryStream);

}

Adding a timestamp to existing PDF document

You can add timestamp to the existing PDF document using the following code snippet.

C#

//Load the existing PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument("Input.pdf");

//Add a new page

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Creates a digital signature

PdfSignature signature = new PdfSignature(page, "Signature");

//Add the time stamp by using the server URI

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

//Saves  the document

loadedDocument.Save("Output.pdf");

//Closes the document

loadedDocument.Close(true);

VB.NET

'Load the PDF document

Dim document As New PdfLoadedDocument("Input.pdf")

'Gets the first page of the document

Dim page As PdfLoadedPage = TryCast(document.Pages(0), PdfLoadedPage)

'Creates a digital signature

Dim signature As New PdfSignature(page, "Signature")

'Adds time stamp by using the server URI

signature.TimeStampServer = New TimeStampServer(New Uri("http://syncfusion.digistamp.com"), "user", "123456")

'Saves and closes the document

document.Save("Output.pdf")

document.Close(True)

UWP

//Create the file open picker 

var picker = new FileOpenPicker();

picker.FileTypeFilter.Add(".pdf");

//Browse and chose the file 

StorageFile file = await picker.PickSingleFileAsync();

//Creates an empty PDF loaded document instance

PdfLoadedDocument loadedDocument = new PdfLoadedDocument();

//Loads or opens an existing PDF document through Open method of PdfLoadedDocument class

await loadedDocument.OpenAsync(file);

//Gets the first page of the document

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Creates a digital signature

PdfSignature signature = new PdfSignature(page, "Signature");

//Add the time stamp by using the server URI

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

MemoryStream stream = new MemoryStream();

await loadedDocument.SaveAsync(stream);

//Close the document. 

loadedDocument.Close(true);

//Save the stream as PDF document file in local machine. Refer to PDF/UWP section for respected code samples

Save(stream, "Output.pdf");

ASP.NET Core

//Load the PDF document

FileStream docStream = new FileStream("Input.pdf", FileMode.Open, FileAccess.Read);

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(docStream);

//Gets the page

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Creates a digital signature.

PdfSignature signature = new PdfSignature(page, "Signature");

//Add the time stamp by using the server URI

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

//Save the document into stream

MemoryStream stream = new MemoryStream();

loadedDocument.Save(stream);

stream.Position = 0;

//Close the document

loadedDocument.Close(true);

//Defining the ContentType for pdf file

string contentType = "application/pdf";

//Define the file name

string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name

return File(stream, contentType, fileName);

Xamarin

//Load the file as stream

Stream docStream = typeof(App).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Input.pdf ");

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(docStream);  

//Gets the page

PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;

//Creates a digital signature

PdfSignature signature = new PdfSignature(page, "Signature");

//Add the time stamp by using the server URI

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456")

//Save the PDF document to stream

MemoryStream memoryStream = new MemoryStream();

loadedDocument.Save(memoryStream);

//Closes the document

loadedDocument.Close(true);

//Save the stream into PDF file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)

{

    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", memoryStream);

}

else

{

    Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", memoryStream);

}

Retrieve certificate details from an existing signed PDF document

The Essential PDF provides support to get the certificate details from an existing signed PDF document such as,

• Signed date
• Expiry date
• Signed name
• Subject name
• Issuer name
• Certificate distinguished names (country, state, street, email, organization, organization unit, locality, and more).

You can get the above certificate details from an existing signed PDF document by using the following code snippet.

C#

//Load the existing signed PDF

PdfLoadedDocument loadedDocument = new PdfLoadedDocument("SignedDocument.pdf");

//Load the PDF form

PdfLoadedForm loadedForm = loadedDocument.Form as PdfLoadedForm;

//Get the signature field

PdfLoadedSignatureField signatureField = loadedForm.Fields[0] as PdfLoadedSignatureField;

//Get the certificate

PdfCertificate certificate = signatureField.Signature.Certificate;

//Get the signed date

DateTime date = signatureField.Signature.SignedDate;

//Get the signed name

string name = signatureField.Signature.SignedName;

//Get the certificate names based on their distinguished name.

string subjectName = certificate.SubjectName;

string subjectCountry = certificate.GetValue(PdfCertificateDistinguishedName.Country, PdfCertificateField.Subject);

string subjectOrganization = certificate.GetValue(PdfCertificateDistinguishedName.Organization, PdfCertificateField.Subject);

//Issuer details

string issuerName = certificate.IssuerName;

string issuerOrganization = certificate.GetValue(PdfCertificateDistinguishedName.Organization, PdfCertificateField.Issuer);

string issuerCountry = certificate.GetValue(PdfCertificateDistinguishedName.Country, PdfCertificateField.Issuer);

//Get certificate validation date information

DateTime validFrom = certificate.ValidFrom;

DateTime validTo = certificate.ValidTo;

//Close the document

loadedDocument.Close(true);

VB.NET

'Load the existing signed PDF

Dim loadedDocument As PdfLoadedDocument = New PdfLoadedDocument("../../Signed.pdf")

'Load the PDF form

Dim loadedForm As PdfLoadedForm = TryCast(loadedDocument.Form, PdfLoadedForm)

'Get the signature field

Dim signatureField As PdfLoadedSignatureField = TryCast(loadedForm.Fields(0), PdfLoadedSignatureField)

'Get the certificate

Dim certificate As PdfCertificate = signatureField.Signature.Certificate

'Get the signed date

Dim signedDate As DateTime = signatureField.Signature.SignedDate

'Get the signed name

Dim name As String = signatureField.Signature.SignedName

'Get the certificate names based on their distinguished name

Dim subjectName As String = certificate.SubjectName

Dim subjectCountry As String = certificate.GetValue(PdfCertificateDistinguishedName.Country, PdfCertificateField.Subject)

Dim subjectOrganization As String = certificate.GetValue(PdfCertificateDistinguishedName.Organization, PdfCertificateField.Subject)

'Issuer details

Dim issuerName As String = certificate.IssuerName

Dim issuerOrganization As String = certificate.GetValue(PdfCertificateDistinguishedName.Organization, PdfCertificateField.Issuer)

Dim issuerCountry As String = certificate.GetValue(PdfCertificateDistinguishedName.Country, PdfCertificateField.Issuer)

'Get certificate validation date information

Dim validFrom As DateTime = certificate.ValidFrom

Dim validTo As DateTime = certificate.ValidTo

loadedDocument.Close(True)

UWP

//Essential PDF supports retrieving certificate details from signed PDF document only in Windows Forms, WPF, ASP.NET, and ASP.NET MVC platforms

ASP.NET Core

//Load the PDF document

FileStream docStream = new FileStream("Input.pdf", FileMode.Open, FileAccess.Read);

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(docStream);

//Get the signature field

PdfLoadedSignatureField signatureField = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

//Get the certificate

PdfCertificate certificate = signatureField.Signature.Certificate;

//Get the signed date

DateTime date = signatureField.Signature.SignedDate;

//Get the signed name

string name = signatureField.Signature.SignedName;

//Gets the certificate subject's name

string subjectName = certificate.SubjectName;

//Gets the certificate issuer's name

string issuerName = certificate.IssuerName;

//Get certificate validation date information

DateTime validFrom = certificate.ValidFrom;

DateTime validTo = certificate.ValidTo;

//Close the document

loadedDocument.Close(true);

Xamarin

//Essential PDF supports retrieving certificate details from signed PDF document only in Windows Forms, WPF, ASP.NET, and ASP.NET MVC platforms

Enable Long Term Validation (LTV) PDF signature

The Essential PDF supports creating long term signature validation when signing the PDF document. The LTV signature allows you to check the validity of a signature long after the document was signed. To achieve long term validation, all the required elements for signature validation must be embedded in the signed PDF.

NOTE

The resulted PDF document size will be large since all the necessary signature information, Certificate Revocation List (CRL), and Online Certificate Status Protocol (OCSP) are embedded.

The following code example explains how to create LTV PDF.

C#

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPage page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

PdfCertificate pdfCert = new PdfCertificate(@"PDF.pfx", "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(page, pdfCert, "Signature");

//Sets an image for signature field

PdfBitmap image = new PdfBitmap(@"syncfusion_logo.jpeg");

//Adds time stamp by using the server URI and credentials

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

//Enable LTV on Signature

signature.EnableLtv = true;

//Sets signature info 

signature.Bounds = new RectangleF(new PointF(0, 0), image.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(image, 0, 0);

//Saves and closes the document

document.Save("Output.pdf");

document.Close(true);

VB.NET

'Creates a new PDF document

Dim document As New PdfDocument()

'Adds a new page

Dim page As PdfPage = document.Pages.Add()

Dim graphics As PdfGraphics = page.Graphics

'Creates a certificate instance from PFX file with private key

Dim pdfCert As New PdfCertificate("PDF.pfx", "password123")

'Creates a digital signature

Dim signature As New PdfSignature(page, pdfCert, "Signature")

'Sets an image for signature field

Dim image As New PdfBitmap("syncfusion_logo.jpeg")

'Adds time stamp by using the server URI and credentials

signature.TimeStampServer = New TimeStampServer(New Uri("http://syncfusion.digistamp.com"), "user", "123456")

'Enable LTV on Signature

signature.EnableLtv = True

'Sets signature info

signature.Bounds = New RectangleF(New PointF(0, 0), image.PhysicalDimension)

signature.ContactInfo = "[e-mail]"

signature.LocationInfo = "Honolulu, Hawaii"

signature.Reason = "I am author of this document."

'Draws the signature image

graphics.DrawImage(image, 0, 0)

'Saves and closes the document

document.Save("Output.pdf")

document.Close(True)

UWP

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.syncfusion_logo.jpeg");

PdfBitmap image = new PdfBitmap(imageStream);

//Adds time stamp by using the server URI and credentials

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

//Enable LTV on Signature

signature.EnableLtv = true;

//Sets signature info

signature.Bounds = new RectangleF(new PointF(0, 0), image.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(image, 0, 0);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

await document.SaveAsync(stream);

//Close the document

document.Close(true);

//Save the stream as PDF document file in local machine. Refer to PDF/UWP section for respected code samples

Save(stream, "output.pdf");

ASP.NET Core

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

FileStream certificateStream = new FileStream("PDF.pfx", FileMode.Open, FileAccess.Read);

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

FileStream imageStream = new FileStream("syncfusion_logo.jpeg", FileMode.Open, FileAccess.Read);

//Sets an image for signature field

PdfBitmap image = new PdfBitmap(imageStream);

//Adds time stamp by using the server URI and credentials

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

//Enable LTV on Signature

signature.EnableLtv = true;

//Sets signature info

signature.Bounds = new RectangleF(new PointF(0, 0), image.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(image, 0, 0);

//Save the document into stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

stream.Position = 0;

//Close the documents

document.Close(true);

//Defining the ContentType for pdf file

string contentType = "application/pdf";

//Define the file name

string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name

return File(stream, contentType, fileName);

Xamarin

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.syncfusion_logo.jpeg");

PdfBitmap image = new PdfBitmap(imageStream);

//Adds time stamp by using the server URI and credentials

signature.TimeStampServer = new TimeStampServer(new Uri("http://syncfusion.digistamp.com"), "user", "123456");

//Enable LTV on Signature

signature.EnableLtv = true;

//Sets signature info

signature.Bounds = new RectangleF(new PointF(0, 0), image.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(image, 0, 0);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

//Closes the document

document.Close(true);

//Save the stream into PDF file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)

{

    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("output.pdf", "application/pdf", stream);

}

else

{
 
 Xamarin.Forms.DependencyService.Get<ISave>().Save("output.pdf", "application/pdf", stream);

}

Adding a digital signature with customization

The PdfSignatureSettings allows you to add customized digital signatures to the PDF document.

Adding a digital signature with CAdES format

As per the PDF specification 2.0, now Syncfusion PDF library supports digital signature based on CAdES (CMS Advanced Electronics Signature). The CAdES based digital signature can remain valid for long periods, even if underlying cryptographic algorithms are broken. Using the API CryptographicStandard, you can change the standard between CMS (Cryptographic Message Syntax) and CAdES.

The following code example explains how to add a digital signature with cryptographic standard (CAdES) to the PDF document.

C#

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

PdfCertificate pdfCert = new PdfCertificate(@"PDF.pfx", "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets signature settings to customize cryptographic standard specified

PdfSignatureSettings settings = signature.Settings;

settings.CryptographicStandard  = CryptographicStandard.CADES;

//Sets an image for signature field

PdfBitmap signatureImage = new PdfBitmap(@"signature.jpg");

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Saves and closes the document

document.Save("Output.pdf");

document.Close(true);

VB.NET

'Creates a new PDF document

Dim document As New PdfDocument()

'Adds a new page

Dim page As PdfPageBase = document.Pages.Add()

Dim graphics As PdfGraphics = page.Graphics

'Creates a certificate instance from PFX file with private key

Dim pdfCert As New PdfCertificate("PDF.pfx", "password123")

'Creates a digital signature

Dim signature As New PdfSignature(document, page, pdfCert, "Signature")

'Sets signature settings to customize cryptographic standard specified

Dim settings As PdfSignatureSettings = signature.Settings

settings.CryptographicStandard  = CryptographicStandard.CADES

'Sets an image for signature field

Dim signatureImage As New PdfBitmap("signature.jpg")

'Sets signature info

signature.Bounds = New RectangleF(New PointF(0, 0), signatureImage.PhysicalDimension)

signature.ContactInfo = "[e-mail]"

signature.LocationInfo = "Honolulu, Hawaii"

signature.Reason = "I am author of this document."

'Draws the signature image

graphics.DrawImage(signatureImage, 0, 0)

'Saves and closes the document

document.Save("Output.pdf")

document.Close(True)

UWP

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets signature settings to customize cryptographic standard specified

PdfSignatureSettings settings = signature.Settings;

settings.CryptographicStandard  = CryptographicStandard.CADES;

//Sets an image for signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.signature.jpg");

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

await document.SaveAsync(stream);

//Close the document

document.Close(true);                                                                   

//Save the stream as PDF document file in local machine. Refer to the PDF/UWP section for respective code samples

Save(stream, "Output.pdf");

ASP.NET Core

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

FileStream certificateStream = new FileStream("PDF.pfx", FileMode.Open, FileAccess.Read);

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets signature settings to customize cryptographic standard specified

PdfSignatureSettings settings = signature.Settings;

settings.CryptographicStandard  = CryptographicStandard.CADES;

//Sets an image for signature field

FileStream imageStream = new FileStream("signature.jpg", FileMode.Open, FileAccess.Read);

//Sets an image for signature field

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the document into stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

stream.Position = 0;

//Close the documents

document.Close(true);

//Defining the ContentType for pdf file

string contentType = "application/pdf";

//Define the file name

string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name

return File(stream, contentType, fileName);

Xamarin

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets signature settings to customize cryptographic standard specified

PdfSignatureSettings settings = signature.Settings;

settings.CryptographicStandard  = CryptographicStandard.CADES;

//Sets an image for signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.signature.jpg");

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

//Closes the document

document.Close(true);

//Save the stream into PDF file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)

{

    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", stream);

}

else

{

    Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", stream);

}

Customize digestion algorithm

In addition, you can now set the different message digest algorithm to sign PDF document using the DigestAlgorithm enum available in the class PdfSignatureSettings.

The following message digest algorithms are now supported:

• SHA1
• SHA256
• SHA384
• SHA512
• RIPEMD160

The following code example explains how to add a digital signature with various digest algorithms to the PDF document.

C#

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

PdfCertificate pdfCert = new PdfCertificate(@"PDF.pfx", "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets signature settings to customize digest algorithm specified

PdfSignatureSettings settings = signature.Settings;

settings.DigestAlgorithm = DigestAlgorithm.SHA256;

//Sets an image for signature field

PdfBitmap signatureImage = new PdfBitmap(@"signature.jpg");

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Saves and closes the document

document.Save("Output.pdf");

document.Close(true);

VB.NET

'Creates a new PDF document

Dim document As New PdfDocument()

'Adds a new page

Dim page As PdfPageBase = document.Pages.Add()

Dim graphics As PdfGraphics = page.Graphics

'Creates a certificate instance from PFX file with private key

Dim pdfCert As New PdfCertificate("PDF.pfx", "password123")

'Creates a digital signature

Dim signature As New PdfSignature(document, page, pdfCert, "Signature")

'Sets signature settings to customize digest algorithm specified

Dim settings As PdfSignatureSettings = signature.Settings

settings.DigestAlgorithm = DigestAlgorithm.SHA256

'Sets an image for signature field

Dim signatureImage As New PdfBitmap("signature.jpg")

'Sets signature info

signature.Bounds = New RectangleF(New PointF(0, 0), signatureImage.PhysicalDimension)

signature.ContactInfo = "[e-mail]"

signature.LocationInfo = "Honolulu, Hawaii"

signature.Reason = "I am author of this document."

'Draws the signature image

graphics.DrawImage(signatureImage, 0, 0)

'Saves and closes the document

document.Save("Output.pdf")

document.Close(True)

UWP

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets signature settings to customize digest algorithm specified

PdfSignatureSettings settings = signature.Settings;

settings.DigestAlgorithm = DigestAlgorithm.SHA256;

//Sets an image for signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.signature.jpg");

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

await document.SaveAsync(stream);

//Close the document

document.Close(true);                                                                   

//Save the stream as PDF document file in local machine. Refer to the PDF/UWP section for respective code samples

Save(stream, "Output.pdf");

ASP.NET Core

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

FileStream certificateStream = new FileStream("PDF.pfx", FileMode.Open, FileAccess.Read);

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets signature settings to customize digest algorithm specified

PdfSignatureSettings settings = signature.Settings;

settings.DigestAlgorithm = DigestAlgorithm.SHA256;

//Sets an image for signature field

FileStream imageStream = new FileStream("signature.jpg", FileMode.Open, FileAccess.Read);

//Sets an image for signature field

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the document into stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

stream.Position = 0;

//Close the documents

document.Close(true);

//Defining the ContentType for pdf file

string contentType = "application/pdf";

//Define the file name

string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name

return File(stream, contentType, fileName);

Xamarin

//Creates a new PDF document

PdfDocument document = new PdfDocument();

//Adds a new page

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Creates a digital signature

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets signature settings to customize digest algorithm specified

PdfSignatureSettings settings = signature.Settings;

settings.DigestAlgorithm = DigestAlgorithm.SHA256;

//Sets an image for signature field

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.signature.jpg");

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Sets signature information

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Draws the signature image

graphics.DrawImage(signatureImage, 0, 0);

//Save the PDF document to stream

MemoryStream stream = new MemoryStream();

document.Save(stream);

//Closes the document

document.Close(true);

//Save the stream into PDF file

//The operation in Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)

{

    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", stream);

}

else

{

    Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", stream);

}

Digital signature validation

Added the support to validate the digital signatures in an existing PDF document. Digital signature validation covers the following steps to ensure the validity of the signatures:

• Validate the document modification.
• Validate the certificate chain.
• Ensure the signature with timestamp time.
• Check the revocation status of the certificate with OCSP and CRL.
• Ensure the multiple digital signatures.

You can use the ValidateSignature method available in the PdfLoadedSignatureField class to validate the digital signature.

You can get the overall status from the IsSignatureValid property available in the PdfSignatureValidationResult class.

The following code example explains how to validate the digitally signed PDF document signature.

C#

//Load an existing signed PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument("Input.pdf");

//Get signature field

PdfLoadedSignatureField signatureField = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

//X509Certificate2Collection to check the signer's identity using root certificates

X509CertificateCollection collection = new X509CertificateCollection();

//Create new X509Certificate2 with the root certificate

X509Certificate2 certificate = new X509Certificate2("PDF.pfx", "password123");

//Add the certificate to the collection

collection.Add(certificate);

//Validate signature and get the validation result

PdfSignatureValidationResult result = signatureField.ValidateSignature(collection);

//Checks whether the signature is valid or not

SignatureStatus status = result.SignatureStatus;

//Checks whether the document is modified or not

bool isModified = result.IsDocumentModified;

//Signature details

string issuerName = signatureField.Signature.Certificate.IssuerName;

DateTime validFrom = signatureField.Signature.Certificate.ValidFrom;

DateTime validTo = signatureField.Signature.Certificate.ValidTo;

string signatureAlgorithm = result.SignatureAlgorithm;

DigestAlgorithm digestAlgorithm = result.DigestAlgorithm;

//Revocation validation details

RevocationResult revocationDetails = result.RevocationResult;

RevocationStatus revocationStatus = revocationDetails.OcspRevocationStatus;

bool isRevokedCRL = revocationDetails.IsRevokedCRL;

//Close the document

loadedDocument.Close(true);

VB.NET

'Load an existing signed PDF document

Dim loadedDocument As PdfLoadedDocument = New PdfLoadedDocument("Input.pdf")

'Get signature field

Dim signatureField As PdfLoadedSignatureField = loadedDocument.Form.Fields[0] As PdfLoadedSignatureField

'X509Certificate2Collection to check the signer's identity using root certificates

Dim collection As X509CertificateCollection = New X509CertificateCollection()

'Create new X509Certificate2 with the root certificate

Dim certificate As X509Certificate2 = New X509Certificate2("PDF.pfx", "password123")

'Add the certificate to the collection

collection.Add(certificate)

'Validate signature and get the validation result

Dim result As PdfSignatureValidationResult = signatureField.ValidateSignature(collection)

'Checks whether the signature is valid or not

Dim status As SignatureStatus = result.SignatureStatus

'Checks whether the document is modified or not

Dim isModified As Boolean = result.IsDocumentModified

'Signature details

Dim issuerName As String = signatureField.Signature.Certificate.IssuerName

Dim validFrom As DateTime = signatureField.Signature.Certificate.ValidFrom

Dim validTo As DateTime = signatureField.Signature.Certificate.ValidTo

Dim signatureAlgorithm As String = result.SignatureAlgorithm

Dim digestAlgorithm As DigestAlgorithm = result.DigestAlgorithm

'Revocation validation details

Dim revocationDetails As RevocationResult = result.RevocationResult

Dim revocationStatus As RevocationStatus = revocationDetails.OcspRevocationStatus

Dim isRevokedCRL As Boolean = revocationDetails.IsRevokedCRL

'Close the document

loadedDocument.Close(true)

UWP

//Get the stream from the document

Stream documentStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.Input.pdf");

//Load an existing signed PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//Get signature field

PdfLoadedSignatureField signatureField = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

//X509Certificate2Collection to check the signer's identity using root certificates

X509CertificateCollection collection = new X509CertificateCollection();

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.PDF.pfx");

byte[] data = new byte[certificateStream.Length];

certificateStream.Read(data, 0, data.Length);

//Create new X509Certificate2 with the root certificate

X509Certificate2 certificate = new X509Certificate2(data, "password123");

//Add the certificate to the collection

collection.Add(certificate);

//Validate signature and get the validation result

PdfSignatureValidationResult result = signatureField.ValidateSignature(collection);

//Checks whether the signature is valid or not

SignatureStatus status = result.SignatureStatus;

//Checks whether the document is modified or not

bool isModified = result.IsDocumentModified;

//Signature details

string issuerName = signatureField.Signature.Certificate.IssuerName;

DateTime validFrom = signatureField.Signature.Certificate.ValidFrom;

DateTime validTo = signatureField.Signature.Certificate.ValidTo;

string signatureAlgorithm = result.SignatureAlgorithm;

DigestAlgorithm digestAlgorithm = result.DigestAlgorithm;

//Revocation validation details

RevocationResult revocationDetails = result.RevocationResult;

RevocationStatus revocationStatus = revocationDetails.OcspRevocationStatus;

bool isRevokedCRL = revocationDetails.IsRevokedCRL;

//Close the document

loadedDocument.Close(true);

ASP.NET Core

//Get the stream from the document

FileStream documentStream = new FileStream("Input.pdf", FileMode.Open, FileAccess.Read);

//Load an existing signed PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//Get signature field

PdfLoadedSignatureField signatureField = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

//X509Certificate2Collection to check the signer's identity using root certificates

X509CertificateCollection collection = new X509CertificateCollection();

//Creates a certificate instance from PFX file with private key

FileStream certificateStream = new FileStream("PDF.pfx", FileMode.Open, FileAccess.Read);

byte[] data = new byte[certificateStream.Length];

certificateStream.Read(data, 0, data.Length);

//Create new X509Certificate2 with the root certificate

X509Certificate2 certificate = new X509Certificate2(data, "password123");

//Add the certificate to the collection

collection.Add(certificate);

//Validate signature and get the validation result

PdfSignatureValidationResult result = signatureField.ValidateSignature(collection);

//Checks whether the signature is valid or not

SignatureStatus status = result.SignatureStatus;

//Checks whether the document is modified or not

bool isModified = result.IsDocumentModified;

//Signature details

string issuerName = signatureField.Signature.Certificate.IssuerName;

DateTime validFrom = signatureField.Signature.Certificate.ValidFrom;

DateTime validTo = signatureField.Signature.Certificate.ValidTo;

string signatureAlgorithm = result.SignatureAlgorithm;

DigestAlgorithm digestAlgorithm = result.DigestAlgorithm;

//Revocation validation details

RevocationResult revocationDetails = result.RevocationResult;

RevocationStatus revocationStatus = revocationDetails.OcspRevocationStatus;

bool isRevokedCRL = revocationDetails.IsRevokedCRL;

//Close the document

loadedDocument.Close(true);

Xamarin

//Get the stream from the document

Stream documentStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Input.pdf");

//Load an existing signed PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//Get signature field

PdfLoadedSignatureField signatureField = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

//X509Certificate2Collection to check the signer's identity using root certificates

X509CertificateCollection collection = new X509CertificateCollection();

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF.pfx");

byte[] data = new byte[certificateStream.Length];

certificateStream.Read(data, 0, data.Length);

//Create new X509Certificate2 with the root certificate

X509Certificate2 certificate = new X509Certificate2(data, "password123");

//Add the certificate to the collection

collection.Add(certificate);

//Validate signature and get the validation result

PdfSignatureValidationResult result = signatureField.ValidateSignature(collection);

//Checks whether the signature is valid or not

SignatureStatus status = result.SignatureStatus;

//Checks whether the document is modified or not

bool isModified = result.IsDocumentModified;

//Signature details

string issuerName = signatureField.Signature.Certificate.IssuerName;

DateTime validFrom = signatureField.Signature.Certificate.ValidFrom;

DateTime validTo = signatureField.Signature.Certificate.ValidTo;

string signatureAlgorithm = result.SignatureAlgorithm;

DigestAlgorithm digestAlgorithm = result.DigestAlgorithm;

//Revocation validation details

RevocationResult revocationDetails = result.RevocationResult;

RevocationStatus revocationStatus = revocationDetails.OcspRevocationStatus;

bool isRevokedCRL = revocationDetails.IsRevokedCRL;

//Close the document

loadedDocument.Close(true);

Validate all signatures in PDF document

Added the support to validate all the digital signatures in an existing PDF document.

You can use the ValidateSignatures method available in the PdfLoadedFormFieldCollection class to validate all the digital signatures. You can get the list of PdfSignatureValidationResult from the ValidateSignatures method.

The following code example explains how to validate all the signatures in digitally signed PDF document.

C#

//Load an existing signed PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument("Input.pdf");

//X509Certificate2Collection to check the signer's identity using root certificates

X509CertificateCollection collection = new X509CertificateCollection();

//Create new X509Certificate2 with the root certificate

X509Certificate2 certificate = new X509Certificate2("PDF.pfx", "password123");

//Add the certificate to the collection

collection.Add(certificate);

//Validate all signatures in loaded PDF document and get the list of validation result

List<PdfSignatureValidationResult> results;

bool isValid = loadedDocument.Form.Fields.ValidateSignatures(collection, out results);

//Close the document

loadedDocument.Close(true);

VB.NET

'Load an existing signed PDF document

Dim loadedDocument As PdfLoadedDocument = New PdfLoadedDocument("Input.pdf")

'X509Certificate2Collection to check the signer's identity using root certificates

Dim collection As X509CertificateCollection = New X509CertificateCollection()

'Create new X509Certificate2 with the root certificate

Dim certificate As X509Certificate2 = New X509Certificate2("PDF.pfx", "password123")

'Add the certificate to the collection

collection.Add(certificate)

'Validate all signatures in loaded PDF document and get the list of validation result

Dim results As List<PdfSignatureValidationResult>

Dim isValid As Boolean = loadedDocument.Form.Fields.ValidateSignatures(collection, out results)

'Close the document

loadedDocument.Close(true)

UWP

//Get the stream from the document

Stream documentStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.Input.pdf");

//Load an existing signed PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//X509Certificate2Collection to check the signer's identity using root certificates

X509CertificateCollection collection = new X509CertificateCollection();

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.PDF.pfx");

byte[] data = new byte[certificateStream.Length];

certificateStream.Read(data, 0, data.Length);

//Create new X509Certificate2 with the root certificate

X509Certificate2 certificate = new X509Certificate2(data, "password123");

//Add the certificate to the collection

collection.Add(certificate);

//Validate all signatures in loaded PDF document and get the list of validation result

List<PdfSignatureValidationResult> results;

bool isValid = loadedDocument.Form.Fields.ValidateSignatures(collection, out results);

//Close the document

loadedDocument.Close(true);

ASP.NET Core

//Get the stream from the document

FileStream documentStream = new FileStream("Input.pdf", FileMode.Open, FileAccess.Read);

//Load an existing signed PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//X509Certificate2Collection to check the signer's identity using root certificates

X509CertificateCollection collection = new X509CertificateCollection();

//Creates a certificate instance from PFX file with private key

FileStream certificateStream = new FileStream("PDF.pfx", FileMode.Open, FileAccess.Read);

byte[] data = new byte[certificateStream.Length];

certificateStream.Read(data, 0, data.Length);

//Create new X509Certificate2 with the root certificate

X509Certificate2 certificate = new X509Certificate2(data, "password123");

//Add the certificate to the collection

collection.Add(certificate);

//Validate all signatures in loaded PDF document and get the list of validation result

List<PdfSignatureValidationResult> results;

bool isValid = loadedDocument.Form.Fields.ValidateSignatures(collection, out results);

//Close the document

loadedDocument.Close(true);

Xamarin

//Get the stream from the document

Stream documentStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Input.pdf");

//Load an existing signed PDF document

PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//X509Certificate2Collection to check the signer's identity using root certificates

X509CertificateCollection collection = new X509CertificateCollection();

//Creates a certificate instance from PFX file with private key

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF.pfx");

byte[] data = new byte[certificateStream.Length];

certificateStream.Read(data, 0, data.Length);

//Create new X509Certificate2 with the root certificate

X509Certificate2 certificate = new X509Certificate2(data, "password123");

//Add the certificate to the collection

collection.Add(certificate);

//Validate all signatures in loaded PDF document and get the list of validation result

List<PdfSignatureValidationResult> results;

bool isValid = loadedDocument.Form.Fields.ValidateSignatures(collection, out results);

//Close the document

loadedDocument.Close(true);

Deferred signing in PDF document

The following code sample shows how to be deferred signing in a PDF document from an external signature.

Steps for deferred signing:

1. Create a PDF document with an empty signature.
2. Users will sign the document hash using the external services.
3. Replace the empty signature with a signed hash from the external services.

C#

//Load an existing PDF document.
PdfLoadedDocument loadedDocument = new PdfLoadedDocument("PDF_Succinctly.pdf");

//Creates a digital signature.
PdfSignature signature = new PdfSignature(loadedDocument, loadedDocument.Pages[0], null, "Signature");

//Sets the signature information.
signature.Bounds = new RectangleF(new PointF(0, 0), new SizeF(100, 30));
signature.Settings.CryptographicStandard = CryptographicStandard.CADES;
signature.Settings.DigestAlgorithm = DigestAlgorithm.SHA1;

//Create an external signer.
IPdfExternalSigner externalSignature = new SignEmpty("SHA1");

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> certificates = new System.Collections.Generic.List<X509Certificate2>();
certificates.Add(new X509Certificate2(Convert.FromBase64String(PublicCert)));
signature.AddExternalSigner(externalSignature, certificates, null);

//Saves the document.
loadedDocument.Save("EmptySignature.pdf");

//Closes the document.
loadedDocument.Close(true);


/// <summary>
/// Represents to sign an empty signature from an external signer.
/// </summary>
class SignEmpty : IPdfExternalSigner
{        
private string _hashAlgorithm;

public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public SignEmpty(string hashAlgorithm)
{
_hashAlgorithm = hashAlgorithm;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Send the document hash for signing using the external services.
SignDocumentHash(message);
//Set a null value to create an empty signed document.
byte[] signedBytes = null;
timeStampResponse = null;
return signedBytes;
}        
}

//Create an external signer with a signed hash message.
IPdfExternalSigner externalSigner = new ExternalSigner("SHA1", signedHash);

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> publicCertificates = new System.Collections.Generic.List<X509Certificate2>();
publicCertificates.Add(new X509Certificate2(Convert.FromBase64String(PublicCert)));

//Create an output file stream.
MemoryStream outputFileStream = new MemoryStream();    

// Get the stream from the document
FileStream inputFileStream = new FileStream("EmptySignature.pdf", FileMode.Open, FileAccess.Read);

string pdfPassword = string.Empty;

//Replace an empty signature.
PdfSignature.ReplaceEmptySignature(inputFileStream, pdfPassword, outputFileStream, signatureName, externalSigner, publicCertificates);


/// <summary>
/// Represents to replace an empty signature from an external signer.
/// </summary>
class ExternalSigner : IPdfExternalSigner
{       
private string _hashAlgorithm;
private byte[] _signedHash;
public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public ExternalSigner(string hashAlgorithm, byte[] hash)
{
_hashAlgorithm = hashAlgorithm;
_signedHash = hash;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Set the signed hash message to replace an empty signature.
byte[] signedBytes = _signedHash;            
timeStampResponse = null;
return signedBytes;
}
}

VB.NET

'Load an existing PDF document.
Dim loadedDocument As PdfLoadedDocument = New PdfLoadedDocument("PDF_Succinctly.pdf")

'Creates a digital signature.
Dim signature As PdfSignature = New PdfSignature(loadedDocument, loadedDocument.Pages(0), Nothing, "Signature")

'Sets the signature information.
signature.Bounds = New RectangleF(New PointF(0, 0), New SizeF(100, 30))
signature.Settings.CryptographicStandard = CryptographicStandard.CADES
signature.Settings.DigestAlgorithm = DigestAlgorithm.SHA1

' Create an external signer.
Dim externalSignature As IPdfExternalSigner = New SignEmpty("SHA1")

' Add public certificates.
Dim certificates As System.Collections.Generic.List(Of X509Certificate2) = New System.Collections.Generic.List(Of X509Certificate2)
certificates.Add(New X509Certificate2(Convert.FromBase64String(PublicCert)))
signature.AddExternalSigner(externalSignature, certificates, Nothing)

'Saves the document.
loadedDocument.Save("EmptySignature.pdf")

'Closes the document.
loadedDocument.Close(True)

''' <summary>
''' Represents to sign an empty signature. 
''' </summary>
Class SignEmpty
Implements IPdfExternalSigner

Private _hashAlgorithm As String

Public ReadOnly Property HashAlgorithm As String Implements IPdfExternalSigner.HashAlgorithm
Get
Return Me._hashAlgorithm
End Get
End Property

Public Sub New(ByVal hashAlgorithm As String)
MyBase.New
Me._hashAlgorithm = hashAlgorithm
End Sub

Private Function IPdfExternalSigner_Sign(message() As Byte, ByRef timeStampResponse() As Byte) As Byte() Implements IPdfExternalSigner.Sign
'Send document hash for signing using the external services.
Me.SignDocumentHash(message)
'Set a null value to create an empty signed document.
Dim signedBytes() As Byte = Nothing
timeStampResponse = Nothing
Return signedBytes
End Function

End Class

'Create an external signer with a signed hash message.
Dim externalSigner As IPdfExternalSigner = New ExternalSigner("SHA1", Module1.SignedHash)

'Add public certificates.
Dim publicCertificates As System.Collections.Generic.List(Of X509Certificate2) = New System.Collections.Generic.List(Of X509Certificate2)
publicCertificates.Add(New X509Certificate2(Convert.FromBase64String(PublicCert)))

'Create an output file stream.
Dim outputFileStream As MemoryStream = New MemoryStream

'Get the stream from the document.
Dim documentStream As FileStream = New FileStream("EmptySignature.pdf ", FileMode.Open, FileAccess.Read)
Dim pdfPassword As String = String.Empty
'Replace an empty signature.
PdfSignature.ReplaceEmptySignature(documentStream, pdfPassword, outputFileStream, "Signature", externalSigner, publicCertificates)

''' <summary>
''' Represents to replace the empty signature.
''' </summary>
Class ExternalSigner
Implements IPdfExternalSigner
Private _hashAlgorithm As String
Private _signedHash() As Byte

Public ReadOnly Property HashAlgorithm As String Implements IPdfExternalSigner.HashAlgorithm
Get
Return Me._hashAlgorithm
End Get
End Property

Public Sub New(ByVal hashAlgorithm As String, ByVal hash() As Byte)
MyBase.New
Me._hashAlgorithm = hashAlgorithm
Me._signedHash = hash
End Sub

Private Function IPdfExternalSigner_Sign(message() As Byte, ByRef timeStampResponse() As Byte) As Byte() Implements IPdfExternalSigner.Sign
'Set the signed hash message to replace an empty signature.
Dim signedBytes() As Byte = Me._signedHash
timeStampResponse = Nothing
Return signedBytes
End Function
End Class

UWP

//Get the stream from the document.
Stream documentStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data. PDF_Succinctly.pdf");

//Load an existing PDF document.
PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//Creates a digital signature.
PdfSignature signature = new PdfSignature(loadedDocument, loadedDocument.Pages[0], null, "Signature");

//Sets the signature information.
signature.Bounds = new RectangleF(new PointF(0, 0), new SizeF(100, 30));
signature.Settings.CryptographicStandard = CryptographicStandard.CADES;
signature.Settings.DigestAlgorithm = DigestAlgorithm.SHA1;

//Create an external signer.
IPdfExternalSigner externalSignature = new SignEmpty("SHA1");

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> certificates = new System.Collections.Generic.List<X509Certificate2>();
certificates.Add(new X509Certificate2(Convert.FromBase64String(PublicCert)));
signature.AddExternalSigner(externalSignature, certificates, null);

//Save the document.
MemoryStream stream = new MemoryStream();
loadedDocument.Save(stream);

//Close the PDF document.
loadedDocument.Close(true);

//Save the stream as a PDF document file in the local machine. Refer to the PDF or UWP section for the respected code samples
Save(stream, "EmptySignature.pdf");

/// <summary>
/// Represents to sign an empty signature from an external signer.
/// </summary>
class SignEmpty : IPdfExternalSigner
{        
private string _hashAlgorithm;

public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public SignEmpty(string hashAlgorithm)
{
_hashAlgorithm = hashAlgorithm;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Send document hash for signing using the external services.
SignDocumentHash(message);
//Set a null value to create an empty signed document.
byte[] signedBytes = null;
timeStampResponse = null;
return signedBytes;
}        
}

//Create an external signer with a signed hash message.
IPdfExternalSigner externalSigner = new ExternalSigner("SHA1", signedHash);

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> publicCertificates = new System.Collections.Generic.List<X509Certificate2>();
publicCertificates.Add(new X509Certificate2(Convert.FromBase64String(PublicCert)));

//Create an output file stream.
MemoryStream outputFileStream = new MemoryStream();    

// Get the stream from the document
FileStream inputFileStream = new FileStream("EmptySignature.pdf", FileMode.Open, FileAccess.Read);

string pdfPassword = string.Empty;

//Replace an empty signature.
PdfSignature.ReplaceEmptySignature(inputFileStream, pdfPassword, outputFileStream, signatureName, externalSigner, publicCertificates);


/// <summary>
/// Represents to replace an empty signature from an external signer.
/// </summary>
class ExternalSigner : IPdfExternalSigner
{       
private string _hashAlgorithm;
private byte[] _signedHash;
public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public ExternalSigner(string hashAlgorithm, byte[] hash)
{
_hashAlgorithm = hashAlgorithm;
_signedHash = hash;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Set the signed hash message to replace an empty signature.
byte[] signedBytes = _signedHash;            
timeStampResponse = null;
return signedBytes;
}
}

ASP.NET Core

// Get the stream from the document.
FileStream documentStream = new FileStream("PDF_Succinctly.pdf ", FileMode.Open, FileAccess.Read);

//Load an existing PDF document.
PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//Creates a digital signature.
PdfSignature signature = new PdfSignature(loadedDocument, loadedDocument.Pages[0], null, "Signature");

//Sets the signature information.
signature.Bounds = new RectangleF(new PointF(0, 0), new SizeF(100, 30));
signature.Settings.CryptographicStandard = CryptographicStandard.CADES;
signature.Settings.DigestAlgorithm = DigestAlgorithm.SHA1;

//Create an external signer.
IPdfExternalSigner externalSignature = new SignEmpty("SHA1");

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> certificates = new System.Collections.Generic.List<X509Certificate2>();
certificates.Add(new X509Certificate2(Convert.FromBase64String(PublicCert)));
signature.AddExternalSigner(externalSignature, certificates, null);

//Save the document.
MemoryStream stream = new MemoryStream();
loadedDocument.Save(stream);

//Close the PDF document.
loadedDocument.Close(true);

//Defining the ContentType for a PDF file.
string contentType = "application/pdf";

//Define the file name.
string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name.
return File(stream, contentType, fileName);

/// <summary>
/// Represents to sign an empty signature from the external signer.
/// </summary>
class SignEmpty : IPdfExternalSigner
{        
private string _hashAlgorithm;

public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public SignEmpty(string hashAlgorithm)
{
_hashAlgorithm = hashAlgorithm;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Send document hash for signing using the external services.
SignDocumentHash(message);
//Set a null value to create an empty signed document.
byte[] signedBytes = null;
timeStampResponse = null;
return signedBytes;
}        
}

//Create an external signer with a signed hash message.
IPdfExternalSigner externalSigner = new ExternalSigner("SHA1", signedHash);

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> publicCertificates = new System.Collections.Generic.List<X509Certificate2>();
publicCertificates.Add(new X509Certificate2(Convert.FromBase64String(PublicCert)));

//Create an output file stream.
MemoryStream outputFileStream = new MemoryStream();    

// Get the stream from the document
FileStream inputFileStream = new FileStream("EmptySignature.pdf", FileMode.Open, FileAccess.Read);

string pdfPassword = string.Empty;

//Replace an empty signature.
PdfSignature.ReplaceEmptySignature(inputFileStream, pdfPassword, outputFileStream, signatureName, externalSigner, publicCertificates);


/// <summary>
/// Represents to replace an empty signature from an external signer.
/// </summary>
class ExternalSigner : IPdfExternalSigner
{       
private string _hashAlgorithm;
private byte[] _signedHash;
public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public ExternalSigner(string hashAlgorithm, byte[] hash)
{
_hashAlgorithm = hashAlgorithm;
_signedHash = hash;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Set the signed hash message to replace an empty signature.
byte[] signedBytes = _signedHash;            
timeStampResponse = null;
return signedBytes;
}
}

Xamarin

//Get the stream from the document.
Stream documentStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data. PDF_Succinctly.pdf");

//Load an existing PDF document.
PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//Creates a digital signature.
PdfSignature signature = new PdfSignature(loadedDocument, loadedDocument.Pages[0], null, "Signature");

//Sets the signature information.
signature.Bounds = new RectangleF(new PointF(0, 0), new SizeF(100, 30));
signature.Settings.CryptographicStandard = CryptographicStandard.CADES;
signature.Settings.DigestAlgorithm = DigestAlgorithm.SHA1;

//Create an external signer.
IPdfExternalSigner externalSignature = new SignEmpty("SHA1");

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> certificates = new System.Collections.Generic.List<X509Certificate2>();
certificates.Add(new X509Certificate2(Convert.FromBase64String(PublicCert)));
signature.AddExternalSigner(externalSignature, certificates, null);

//Save the document to the stream.
MemoryStream stream = new MemoryStream();
loadedDocument.Save(stream);

//Close the document.
loadedDocument.Close(true);

stream.Position = 0;

//Save the stream into a PDF file.

//The operation in save under Xamarin varies between Windows Phone, Android, and iOS platforms. Please refer to the PDF/Xamarin section for respective code samples.

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)
{
    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", stream);
}
else
{
    Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", stream);
}

/// <summary>
/// Represents to sign an empty signature from an external signer.
/// </summary>
class SignEmpty : IPdfExternalSigner
{        
private string _hashAlgorithm;

public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public SignEmpty(string hashAlgorithm)
{
_hashAlgorithm = hashAlgorithm;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Send document hash for signing using the external services.
SignDocumentHash(message);
//Set a null value to create an empty signed document.
byte[] signedBytes = null;
timeStampResponse = null;
return signedBytes;
}        
}

//Create an external signer with a signed hash message.
IPdfExternalSigner externalSigner = new ExternalSigner("SHA1", signedHash);

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> publicCertificates = new System.Collections.Generic.List<X509Certificate2>();
publicCertificates.Add(new X509Certificate2(Convert.FromBase64String(PublicCert)));

//Create an output file stream.
MemoryStream outputFileStream = new MemoryStream();    

// Get the stream from the document
FileStream inputFileStream = new FileStream("EmptySignature.pdf", FileMode.Open, FileAccess.Read);

string pdfPassword = string.Empty;

//Replace an empty signature.
PdfSignature.ReplaceEmptySignature(inputFileStream, pdfPassword, outputFileStream, signatureName, externalSigner, publicCertificates);


/// <summary>
/// Represents to replace an empty signature from an external signer.
/// </summary>
class ExternalSigner : IPdfExternalSigner
{       
private string _hashAlgorithm;
private byte[] _signedHash;
public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public ExternalSigner(string hashAlgorithm, byte[] hash)
{
_hashAlgorithm = hashAlgorithm;
_signedHash = hash;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Set the signed hash message to replace an empty signature.
byte[] signedBytes = _signedHash;            
timeStampResponse = null;
return signedBytes;
}
}

A complete working sample can be downloaded from PdfDeferredSigningSample.zip

Adding the estimated size of the signature

The following code sample shows how to add the estimated size of the signature in the PDF document.

C#

//Creating a new PDF Document. 
PdfDocument document = new PdfDocument();

//Adding a new page to the PDF document. 
PdfPageBase page = document.Pages.Add();

//Create a PDF certificate.
PdfCertificate pdfCert = new PdfCertificate(@"PDF.pfx", "password123");

//Add a new signature to the PDF page.
PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

signature.Bounds = new Rectangle(10, 20, 400, 200);

//Sets the estimated size of the signature.
signature.EstimatedSignatureSize = 20000;

//Save the PDF document.
document.Save("Output.pdf");

//Close the PDF document.
document.Close(true);

VB.NET

'Creating a new PDF Document. 
Dim document As PdfDocument =  New PdfDocument() 
 
'Adding a new page to the PDF document. 
Dim page As PdfPageBase =  document.Pages.Add() 
 
'Create a PDF certificate.
Dim pdfCert As PdfCertificate =  New PdfCertificate("PDF.pfx","password123") 
 
'Add a new signature to the PDF page.
Dim signature As PdfSignature =  New PdfSignature(document,page,pdfCert,"Signature") 
 
signature.Bounds = New Rectangle(10, 20, 400, 200)
 
'Sets the estimated size of the signature.
signature.EstimatedSignatureSize = 20000
 
'Save the PDF document.
document.Save("Output.pdf")
 
'Close the PDF document.
document.Close(True)

UWP

//Creating a new PDF Document.
PdfDocument document = new PdfDocument();

//Adding a new page to the PDF document.
PdfPageBase page = document.Pages.Add();

//Creates a certificate instance from the PFX file with a private key.
Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Add a new signature to the PDF page.
PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

signature.Bounds = new Rectangle(10, 20, 400, 200);

//Sets the estimated size of the signature.
signature.EstimatedSignatureSize = 20000;

//Save the document.
MemoryStream stream = new MemoryStream();
document.Save(stream);

//Close the PDF document.
document.Close(true);

//Save the stream as a PDF document file in the local machine. Refer to the PDF or UWP section for the respective code samples.
Save(stream, "Output.pdf");

ASP.NET Core

//Creating a new PDF Document. 
PdfDocument document = new PdfDocument();

//Adding a new page to the PDF document.
PdfPageBase page = document.Pages.Add();

//Creates a certificate instance from the PFX file with a private key.

FileStream certificateStream = new FileStream("PDF.pfx", FileMode.Open, FileAccess.Read);

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123"); 
//Add a new signature to the PDF page.
PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

signature.Bounds = new Rectangle(10, 20, 400, 200);

//Sets the estimated size of the signature.
signature.EstimatedSignatureSize = 20000;

//Creating the stream object.
MemoryStream stream = new MemoryStream();

//Save the document into stream.
document.Save(stream);

//If the position is not set to '0,' then the PDF will be empty.
stream.Position = 0;

//Close the document.
document.Close(true);

//Defining the ContentType for a PDF file.
string contentType = "application/pdf";

//Define the file name.
string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name.
return File(stream, contentType, fileName);

Xamarin

//Creating a new PDF Document. 
PdfDocument document = new PdfDocument();

//Adding a new page to the PDF document. 
PdfPageBase page = document.Pages.Add();

//Creates a certificate instance from the PFX file with a private key.
Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Add a new signature to the PDF page.
PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

signature.Bounds = new Rectangle(10, 20, 400, 200);

//Sets the estimated size of the signature.
signature.EstimatedSignatureSize = 20000;

//Save the document to the stream.
MemoryStream stream = new MemoryStream();
document.Save(stream);

//Close the document.
document.Close(true);

stream.Position = 0;

//Save the stream into a PDF file.

//The operation in save under the Xamarin varies between Windows Phone, Android, and iOS platforms. Please refer to the PDF or Xamarin section for respective code samples.

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)
{
    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", stream);
}
else
{
    Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", stream);
}

Deferred signing without PKCS7 encoding

The following code sample shows deferred signing in a PDF document without PKCS7 encoding from an external signature.

Steps for deferred signing:

1. Create a PDF document with an empty signature.
2. Users will sign the document hash using the external services.
3. Replace the empty signature with a PKCS7 encoded signed hash from the external services.

C#

//Load an existing PDF document.
PdfLoadedDocument loadedDocument = new PdfLoadedDocument("PDF_Succinctly.pdf");

//Creates a digital signature.
PdfSignature signature = new PdfSignature(loadedDocument, loadedDocument.Pages[0], null, "Signature");

//Sets the signature information.
signature.Bounds = new RectangleF(new PointF(0, 0), new SizeF(100, 30));
signature.Settings.CryptographicStandard = CryptographicStandard.CADES;
signature.Settings.DigestAlgorithm = DigestAlgorithm.SHA1;

//Create an external signer.
IPdfExternalSigner externalSignature = new SignEmpty("SHA1");

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> certificates = new System.Collections.Generic.List<X509Certificate2>();
signature.AddExternalSigner(externalSignature, certificates, null);

//Saves a document.
loadedDocument.Save("EmptySignature.pdf");

//Closes a document.
loadedDocument.Close(true);

//Create an external signer with a signed hash message.
IPdfExternalSigner externalSigner = new ExternalSigner("SHA1");

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> publicCertificates = new System.Collections.Generic.List<X509Certificate2>();
publicCertificates.Add(new X509Certificate2(Convert.FromBase64String(PublicCert)));

//Create an output file stream.
MemoryStream outputFileStream = new MemoryStream();

// Get the stream from a document.
FileStream inputFileStream = new FileStream("EmptySignature.pdf", FileMode.Open, FileAccess.Read);

string pdfPassword = string.Empty;

//Deferred signing without PKCS7 encoding.
PdfSignature.ReplaceEmptySignature(inputFileStream, pdfPassword, outputFileStream, signatureName, externalSigner, publicCertificates, false);

/// <summary>
/// Represents to create an empty signature.
/// </summary>
class SignEmpty : IPdfExternalSigner
{
private string _hashAlgorithm;

public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public SignEmpty(string hashAlgorithm)
{
_hashAlgorithm = hashAlgorithm;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Set a null value to create an empty signed document.
byte[] signedBytes = null;
timeStampResponse = null;
return signedBytes;
}
}
/// <summary>
/// Represents to replace an empty signature from an external signer.
/// </summary>
class ExternalSigner : IPdfExternalSigner
{
private string _hashAlgorithm;
public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public ExternalSigner(string hashAlgorithm)
{
_hashAlgorithm = hashAlgorithm;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Set the signed encoded PKCS7 hash message to replace an empty signature.
byte[] signedBytes = EncodedPKCS7Hash;
timeStampResponse = null;
return signedBytes;
}
}

VB.NET

'Load an existing PDF document.
Dim loadedDocument As PdfLoadedDocument = New PdfLoadedDocument("PDF_Succinctly.pdf")

'Creates a digital signature.
Dim signature As PdfSignature = New PdfSignature(loadedDocument, loadedDocument.Pages(0), Nothing, "Signature")

'Sets the signature information.
signature.Bounds = New RectangleF(New PointF(0, 0), New SizeF(100, 30))
signature.Settings.CryptographicStandard = CryptographicStandard.CADES
signature.Settings.DigestAlgorithm = DigestAlgorithm.SHA1

' Create an external signer.
Dim externalSignature As IPdfExternalSigner = New SignEmpty("SHA1")

' Add public certificates.
Dim certificates As System.Collections.Generic.List(Of X509Certificate2) = New System.Collections.Generic.List(Of X509Certificate2)
signature.AddExternalSigner(externalSignature, certificates, Nothing)

'Saves the document.
loadedDocument.Save("EmptySignature.pdf")

'Closes the document.
loadedDocument.Close(True)

'Create an external signer with a signed hash message.
Dim externalSigner As IPdfExternalSigner = New ExternalSigner("SHA1")

'Add public certificates.
Dim publicCertificates As System.Collections.Generic.List(Of X509Certificate2) = New System.Collections.Generic.List(Of X509Certificate2)
publicCertificates.Add(New X509Certificate2(Convert.FromBase64String(PublicCert)))

'Create an output file stream.
Dim outputFileStream As MemoryStream = New MemoryStream

'Get the stream from the document.
Dim documentStream As FileStream = New FileStream("EmptySignature.pdf ", FileMode.Open, FileAccess.Read)
Dim pdfPassword As String = String.Empty
' Deferred signing without PKCS7 encoding 
PdfSignature.ReplaceEmptySignature(documentStream, pdfPassword, outputFileStream, "Signature", externalSigner, publicCertificates, False)


''' <summary>
''' Represents to create an empty signature.
''' </summary>
Class SignEmpty
Implements IPdfExternalSigner

Private _hashAlgorithm As String

Public ReadOnly Property HashAlgorithm As String Implements IPdfExternalSigner.HashAlgorithm
Get
Return Me._hashAlgorithm
End Get
End Property

Public Sub New(ByVal hashAlgorithm As String)
MyBase.New
Me._hashAlgorithm = hashAlgorithm
End Sub

Private Function IPdfExternalSigner_Sign(message() As Byte, ByRef timeStampResponse() As Byte) As Byte() Implements IPdfExternalSigner.Sign
'Set a null value to create an empty signed document.
Dim signedBytes() As Byte = Nothing
timeStampResponse = Nothing
Return signedBytes
End Function

End Class


''' <summary>
''' Represents to replace the empty signature.
''' </summary>
Class ExternalSigner
Implements IPdfExternalSigner
Private _hashAlgorithm As String

Public ReadOnly Property HashAlgorithm As String Implements IPdfExternalSigner.HashAlgorithm
Get
Return Me._hashAlgorithm
End Get
End Property

Public Sub New(ByVal hashAlgorithm As String)
MyBase.New
Me._hashAlgorithm = hashAlgorithm
End Sub

Private Function IPdfExternalSigner_Sign(message() As Byte, ByRef timeStampResponse() As Byte) As Byte() Implements IPdfExternalSigner.Sign
' Set the signed encoded PKCS7 hash message to replace an empty signature.
Dim signedBytes() As Byte = EncodedPKCS7Hash
timeStampResponse = Nothing
Return signedBytes
End Function
End Class

UWP

//Get the stream from a document.
Stream documentStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data. PDF_Succinctly.pdf");

//Load an existing PDF document.
PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//Creates a digital signature.
PdfSignature signature = new PdfSignature(loadedDocument, loadedDocument.Pages[0], null, "Signature");

//Sets the signature information.
signature.Bounds = new RectangleF(new PointF(0, 0), new SizeF(100, 30));
signature.Settings.CryptographicStandard = CryptographicStandard.CADES;
signature.Settings.DigestAlgorithm = DigestAlgorithm.SHA1;

//Create an external signer.
IPdfExternalSigner externalSignature = new SignEmpty("SHA1");

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> certificates = new System.Collections.Generic.List<X509Certificate2>();
signature.AddExternalSigner(externalSignature, certificates, null);

//Save a document.
MemoryStream stream = new MemoryStream();
loadedDocument.Save(stream);

//Close a PDF document.
loadedDocument.Close(true);

//Save the stream as a PDF document file in the local machine. Refer to the PDF or UWP section for the respected code samples
Save(stream, "EmptySignature.pdf");


//Create an external signer with a signed hash message.
IPdfExternalSigner externalSigner = new ExternalSigner("SHA1");

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> publicCertificates = new System.Collections.Generic.List<X509Certificate2>();
publicCertificates.Add(new X509Certificate2(Convert.FromBase64String(PublicCert)));

//Create an output file stream.
MemoryStream outputFileStream = new MemoryStream();    

// Get the stream from the document
FileStream inputFileStream = new FileStream("EmptySignature.pdf", FileMode.Open, FileAccess.Read);

string pdfPassword = string.Empty;

// Deferred signing without PKCS7 encoding.
PdfSignature.ReplaceEmptySignature(inputFileStream, pdfPassword, outputFileStream, signatureName, externalSigner, publicCertificates, false);


/// <summary>
/// Represents to create an empty signature.
/// </summary>
class SignEmpty : IPdfExternalSigner
{        
private string _hashAlgorithm;

public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public SignEmpty(string hashAlgorithm)
{
_hashAlgorithm = hashAlgorithm;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Set a null value to create an empty signed document.
byte[] signedBytes = null;
timeStampResponse = null;
return signedBytes;
}        
}

/// <summary>
/// Represents to replace an empty signature from an external signer.
/// </summary>
class ExternalSigner : IPdfExternalSigner
{       
private string _hashAlgorithm;
public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public ExternalSigner(string hashAlgorithm)
{
_hashAlgorithm = hashAlgorithm;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Set the signed encoded PKCS7 hash message to replace an empty signature. 
byte[] signedBytes = EncodedPKCS7Hash; 
timeStampResponse = null;
return signedBytes;
}
}

ASP.NET Core

// Get the stream from a document.
FileStream documentStream = new FileStream("PDF_Succinctly.pdf ", FileMode.Open, FileAccess.Read);

//Load an existing PDF document.
PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//Creates a digital signature.
PdfSignature signature = new PdfSignature(loadedDocument, loadedDocument.Pages[0], null, "Signature");

//Sets the signature information.
signature.Bounds = new RectangleF(new PointF(0, 0), new SizeF(100, 30));
signature.Settings.CryptographicStandard = CryptographicStandard.CADES;
signature.Settings.DigestAlgorithm = DigestAlgorithm.SHA1;

//Create an external signer.
IPdfExternalSigner externalSignature = new SignEmpty("SHA1");

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> certificates = new System.Collections.Generic.List<X509Certificate2>();
signature.AddExternalSigner(externalSignature, certificates, null);

//Save a document.
MemoryStream stream = new MemoryStream();
loadedDocument.Save(stream);

//Close a PDF document.
loadedDocument.Close(true);

//Defining the ContentType for a PDF file.
string contentType = "application/pdf";

//Define the file name.
string fileName = "Output.pdf";

//Creates a FileContentResult object by using the file contents, content type, and file name.
return File(stream, contentType, fileName);

//Create an external signer with a signed hash message.
IPdfExternalSigner externalSigner = new ExternalSigner("SHA1");

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> publicCertificates = new System.Collections.Generic.List<X509Certificate2>();
publicCertificates.Add(new X509Certificate2(Convert.FromBase64String(PublicCert)));

//Create an output file stream.
MemoryStream outputFileStream = new MemoryStream();    

// Get the stream from a document.
FileStream inputFileStream = new FileStream("EmptySignature.pdf", FileMode.Open, FileAccess.Read);

string pdfPassword = string.Empty;

// Deferred signing without PKCS7 encoding.
PdfSignature.ReplaceEmptySignature(inputFileStream, pdfPassword, outputFileStream, signatureName, externalSigner, publicCertificates, false);

/// <summary>
/// Represents to create an empty signature.
/// </summary>
class SignEmpty : IPdfExternalSigner
{        
private string _hashAlgorithm;

public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public SignEmpty(string hashAlgorithm)
{
_hashAlgorithm = hashAlgorithm;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Set a null value to create an empty signed document.
byte[] signedBytes = null;
timeStampResponse = null;
return signedBytes;
}        
}

/// <summary>
/// Represents to replace an empty signature from an external signer.
/// </summary>
class ExternalSigner : IPdfExternalSigner
{       
private string _hashAlgorithm;
public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public ExternalSigner(string hashAlgorithm)
{
_hashAlgorithm = hashAlgorithm;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Set the signed encoded PKCS7 hash message to replace an empty signature.
byte[] signedBytes = EncodedPKCS7Hash;
timeStampResponse = null;
return signedBytes;
}
}

Xamarin

//Get the stream from a document.
Stream documentStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data. PDF_Succinctly.pdf");

//Load an existing PDF document.
PdfLoadedDocument loadedDocument = new PdfLoadedDocument(documentStream);

//Creates a digital signature.
PdfSignature signature = new PdfSignature(loadedDocument, loadedDocument.Pages[0], null, "Signature");

//Sets the signature information.
signature.Bounds = new RectangleF(new PointF(0, 0), new SizeF(100, 30));
signature.Settings.CryptographicStandard = CryptographicStandard.CADES;
signature.Settings.DigestAlgorithm = DigestAlgorithm.SHA1;

//Create an external signer.
IPdfExternalSigner externalSignature = new SignEmpty("SHA1");

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> certificates = new System.Collections.Generic.List<X509Certificate2>();
signature.AddExternalSigner(externalSignature, certificates, null);

//Save a document to the stream.
MemoryStream stream = new MemoryStream();
loadedDocument.Save(stream);

//Close a document.
loadedDocument.Close(true);

stream.Position = 0;

//Save the stream into a PDF file.

//The operation in save under Xamarin varies between Windows Phone, Android, and iOS platforms. Please refer to the PDF or Xamarin section for respective code samples.

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)
{
    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", stream);
}
else
{
    Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", stream);
}

//Create an external signer with a signed hash message.
IPdfExternalSigner externalSigner = new ExternalSigner("SHA1");

//Add public certificates.
System.Collections.Generic.List<X509Certificate2> publicCertificates = new System.Collections.Generic.List<X509Certificate2>();
publicCertificates.Add(new X509Certificate2(Convert.FromBase64String(PublicCert)));

//Create an output file stream.
MemoryStream outputFileStream = new MemoryStream();    

// Get the stream from the document
FileStream inputFileStream = new FileStream("EmptySignature.pdf", FileMode.Open, FileAccess.Read);

string pdfPassword = string.Empty;

// Deferred signing without PKCS7 encoding.
PdfSignature.ReplaceEmptySignature(inputFileStream, pdfPassword, outputFileStream, signatureName, externalSigner, publicCertificates, false);


/// <summary>
/// Represents to create an empty signature.
/// </summary>
class SignEmpty : IPdfExternalSigner
{        
private string _hashAlgorithm;

public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public SignEmpty(string hashAlgorithm)
{
_hashAlgorithm = hashAlgorithm;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Set a null value to create an empty signed document.
byte[] signedBytes = null;
timeStampResponse = null;
return signedBytes;
}        
}

/// <summary>
/// Represents to replace an empty signature from an external signer.
/// </summary>
class ExternalSigner : IPdfExternalSigner
{       
private string _hashAlgorithm;
public string HashAlgorithm
{
get { return _hashAlgorithm; }
}

public ExternalSigner(string hashAlgorithm)
{
_hashAlgorithm = hashAlgorithm;
}

public byte[] Sign(byte[] message, out byte[] timeStampResponse)
{
//Set the signed encoded PKCS7 hash message to replace an empty signature.
byte[] signedBytes = EncodedPKCS7Hash;
timeStampResponse = null;
return signedBytes;
}
}

Drawing text/image in the Signature Appearance

The following code example illustrates how to draw text/images in a digital appearance as follows:

C#

//Creates a new PDF document.
PdfDocument document = new PdfDocument();

//Adds a new page.
PdfPageBase page = document.Pages.Add();
PdfGraphics graphics = page.Graphics;

//Creates a certificate instance from PFX file with private key.
PdfCertificate pdfCert = new PdfCertificate(@"PDF.pfx", "password123");

//Creates a digital signature.
PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Sets an image for signature field.
PdfBitmap signatureImage = new PdfBitmap(@"signature.png");

//Sets signature information
signature.Bounds = new RectangleF(0,0,200,100);
signature.ContactInfo = "[e-mail]";
signature.LocationInfo = "Honolulu, Hawaii";
signature.Reason = "I am author of this document.";

//Create appearance for the digital siganture
signature.Appearance.Normal.Graphics.DrawImage(signatureImage, signature.Bounds);

//Save the document
document.Save("DigitalSignature.pdf");

//Close the document
document.Close(true);

VB.NET

'Create a new PDF document.

Dim document As New PdfDocument()

'Add a new page.

Dim page As PdfPageBase = document.Pages.Add()

Dim graphics As PdfGraphics = page.Graphics

'Create a certificate instance from a PFX file with a private key.

Dim pdfCert As New PdfCertificate("PDF.pfx", "password123")

'Create a digital signature.

Dim signature As New PdfSignature(document, page, pdfCert, "Signature")

'Set an image for signature field.

Dim signatureImage As New PdfBitmap("signature.jpg")

'Set the signature information.

signature.Bounds = New RectangleF(New PointF(0, 0), signatureImage.PhysicalDimension)

signature.ContactInfo = "[e-mail]"

signature.LocationInfo = "Honolulu, Hawaii"

signature.Reason = "I am author of this document."

'Create appearance for the digital signature.
signature.Appearance.Normal.Graphics.DrawImage(signatureImage, signature.Bounds);

'Save and close the document.

document.Save("Output.pdf")

document.Close(True)

UWP

//Create a new PDF document.

PdfDocument document = new PdfDocument();

//Add a new page.

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Create a certificate instance from a PFX file with a private key.

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Create a digital signature.

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Set an image for signature field.

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.Data.signature.jpg");

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Set the signature information.

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Create appearance for the digital signature.

signature.Appearance.Normal.Graphics.DrawImage(signatureImage, signature.Bounds);

//Save the PDF document to stream.

MemoryStream stream = new MemoryStream();

await document.SaveAsync(stream);

//Close the document.

document.Close(true);                                                                   

//Save the stream as a PDF document file in the local machine. Refer to the PDF/UWP section for the respective code samples.

Save(stream, "Output.pdf");

ASP.NET Core

//Create a new PDF document.

PdfDocument document = new PdfDocument();

//Add a new page.

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Create a certificate instance from a PFX file with a private key.

FileStream certificateStream = new FileStream("PDF.pfx", FileMode.Open, FileAccess.Read);

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Create a digital signature.

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Set an image for signature field.

FileStream imageStream = new FileStream("signature.jpg", FileMode.Open, FileAccess.Read);

//Set an image for signature field.

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Set the signature information.

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Create appearance for the digital signature.

signature.Appearance.Normal.Graphics.DrawImage(signatureImage, signature.Bounds);

//Save the document into stream.

MemoryStream stream = new MemoryStream();

document.Save(stream);

stream.Position = 0;

//Close the document.

document.Close(true);

//Define the ContentType for pdf file.

string contentType = "application/pdf";

//Define the file name.

string fileName = "Output.pdf";

//Create a FileContentResult object by using the file contents, content type, and file name.

return File(stream, contentType, fileName);

Xamarin

//Create a new PDF document.

PdfDocument document = new PdfDocument();

//Add a new page.

PdfPageBase page = document.Pages.Add();

PdfGraphics graphics = page.Graphics;

//Create a certificate instance from a PFX file with a private key.

Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.PDF.pfx");

PdfCertificate pdfCert = new PdfCertificate(certificateStream, "password123");

//Create a digital signature.

PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");

//Set an image for signature field.

Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("Sample.Assets.signature.jpg");

PdfBitmap signatureImage = new PdfBitmap(imageStream);

//Set the signature information.

signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);

signature.ContactInfo = "[e-mail]";

signature.LocationInfo = "Honolulu, Hawaii";

signature.Reason = "I am author of this document.";

//Create appearance for the digital signature.

signature.Appearance.Normal.Graphics.DrawImage(signatureImage, signature.Bounds);

//Save the PDF document to stream.

MemoryStream stream = new MemoryStream();

document.Save(stream);

//Close the document.

document.Close(true);

//Save the stream into PDF file.

//The operation of Save under Xamarin varies between Windows Phone, Android, and iOS platforms. Refer to the PDF/Xamarin section for respective code samples.

if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)
{
    Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("Output.pdf", "application/pdf", stream);
}
else
{
    Xamarin.Forms.DependencyService.Get<ISave>().Save("Output.pdf", "application/pdf", stream);
}