Digital Signature in JavaScript PDF library

12 Dec 202524 minutes to read

The PDF provides support to create, validate, and manage digital signatures in PDF documents, ensuring authenticity, integrity, and security.

Adding a digital signature

This example demonstrates how to add a digital signature to a PDF document using the PdfSignature class. Digital signatures ensure document authenticity and integrity by applying cryptographic standards.

TypeScript
JavaScript
import {PdfDocument, PdfPage, PdfForm, PdfSignatureField, DigestAlgorithm, CryptographicStandard} from '@syncfusion/ej2-pdf';

// Load the document
let document: PdfDocument = new PdfDocument()
// Get the first page of the document
let page: PdfPage = document.addPage();
// Access the PDF form
let form: PdfForm = document.form;
// Create a new signature field
let field: PdfSignatureField = new PdfSignatureField(page, 'Signature', {
    x: 10,
    y: 10,
    width: 100,
    height: 50
});
// Create a new signature using PFX data and private key
let sign: PdfSignature = PdfSignature.create(
    {
        cryptographicStandard: CryptographicStandard.cms,
        digestAlgorithm: DigestAlgorithm.sha256
    },
    certData,
    password
);
// Set the signature to the field
field.setSignature(sign);
// Add the field into PDF form
form.add(field);
// Save the document
document.save('output.pdf');
// Destroy the document
document.destroy();
// Load the document
var document = new ej.pdf.PdfDocument();
// Get the first page of the document
var page = document.addPage();
// Access the PDF form
var form = document.form;
// Create a new signature field
var field = new ej.pdf.PdfSignatureField(page, 'Signature', {x: 10, y: 10, width: 100, height: 50});
// Create a new signature using PFX data and private key
var sign = ej.pdf.PdfSignature.create({cryptographicStandard: ej.pdf.CryptographicStandard.cms, digestAlgorithm: ej.pdf.DigestAlgorithm.sha256}, certData, password);
// Set the signature to the field
field.setSignature(sign);
// Add the field into PDF form
form.add(field);
// Save the document
document.save('output.pdf');
// Destroy the document
document.destroy();

The following code snippet explains how to add a digital signature in an existing PDF document.

TypeScript
JavaScript
import {PdfDocument, PdfPage, PdfForm, PdfSignatureField, DigestAlgorithm, CryptographicStandard} from '@syncfusion/ej2-pdf';

// Load the document
let document: PdfDocument = new PdfDocument(data)
// Get the first page of the document
let page: PdfPage = document.getPage(0);
// Access the PDF form
let form: PdfForm = document.form;
// Create a new signature field
let field: PdfSignatureField = new PdfSignatureField(page, 'Signature', {
    x: 10,
    y: 10,
    width: 100,
    height: 50
});
// Create a new signature using PFX data and private key
let sign: PdfSignature = PdfSignature.create(
    {
        cryptographicStandard: CryptographicStandard.cms,
        digestAlgorithm: DigestAlgorithm.sha256
    },
    certData,
    password
);
// Set the signature to the field
field.setSignature(sign);
// Add the field into PDF form
form.add(field);
// Save the document
document.save('output.pdf');
// Destroy the document
document.destroy();
// Load the document
var document = new ej.pdf.PdfDocument(data);
// Get the first page of the document
var page = document.getPage(0);
// Access the PDF form
var form = document.form;
// Create a new signature field
var field = new ej.pdf.PdfSignatureField(page, 'Signature', {
    x: 10,
    y: 10,
    width: 100,
    height: 50
});
// Create a new signature using PFX data and private key
var sign = ej.pdf.PdfSignature.create(
    {
        cryptographicStandard: ej.pdf.CryptographicStandard.cms,
        digestAlgorithm: ej.pdf.DigestAlgorithm.sha256
    },
    certData,
    password
);
// Set the signature to the field
field.setSignature(sign);
// Add the field into PDF form
form.add(field);
// Save the document
document.save('output.pdf');
// Destroy the document
document.destroy();

Create PDF Signature with External Signing

Syncfusion^® PDF provides support to create a new PDF signature using a callback function for external signing, enabling secure and flexible digital signature workflows.

TypeScript
JavaScript
import {PdfDocument, PdfPage, PdfForm, PdfSignatureField, DigestAlgorithm, CryptographicStandard} from '@syncfusion/ej2-pdf';

// Load the document
let document: PdfDocument = new PdfDocument(data);
// Gets the first page of the document
let page: PdfPage = document.getPage(0);
// Access the PDF form
let form: PdfForm = document.form;
// Create a new signature field
let field: PdfSignatureField = new PdfSignatureField(page, 'Signature', { x: 10, y: 10, width: 100, height: 50 });
// Define a callback function used for external signing
let externalSignatureCallback = (
    data: Uint8Array,
    options: {
        algorithm: DigestAlgorithm,
        cryptographicStandard: CryptographicStandard,
    }
): { signedData: Uint8Array; timestampData?: Uint8Array } => {
    // Implement external signing logic here
    return new Uint8Array(); // Placeholder return
};
// Create a new signature using external signing
let signature: PdfSignature = PdfSignature.create(externalSignatureCallback, {
    cryptographicStandard: CryptographicStandard.cms,
    algorithm: DigestAlgorithm.sha256,
});
// Set the signature to the field
field.setSignature(signature);
// Add the field into PDF form
form.add(field);
// Save the document
document.save('output.pdf');
// Destroy the document
document.destroy();
// Load the document
var document = new ej.pdf.PdfDocument(data);
// Gets the first page of the document
var page = document.getPage(0);
// Access the PDF form
var form = document.form;
// Create a new signature field
var field = new ej.pdf.PdfSignatureField(page, 'Signature', { x: 10, y: 10, width: 100, height: 50 });
// Define a callback function used for external signing
var externalSignatureCallback = (data, options) => {
  // data: Uint8Array
  // options: { algorithm: ej.pdf.DigestAlgorithm, cryptographicStandard: ej.pdf.CryptographicStandard }
  // Implement external signing logic here and return the signed bytes.
  // Example (placeholder): return only the required property 'signedData'
  return { signedData: new Uint8Array() };
};
// Create a new signature using external signing
var signature = ej.pdf.PdfSignature.create(externalSignatureCallback, {
  cryptographicStandard: ej.pdf.CryptographicStandard.cms,
  algorithm: ej.pdf.DigestAlgorithm.sha256
});
// Set the signature to the field
field.setSignature(signature);
// Add the field into PDF form
form.add(field);
// Save the document
document.save('output.pdf');
// Destroy the document
document.destroy();

Create Signature with Public Certificates for External Signing

This example demonstrates how to create a new PDF signature using the PdfSignature class with public certificates for external signing. External signing allows you to implement custom signing logic outside the PDF library while maintaining compliance with cryptographic standards.

TypeScript
JavaScript
import {PdfDocument, PdfPage, PdfForm, PdfSignatureField, DigestAlgorithm, CryptographicStandard} from '@syncfusion/ej2-pdf';

// Load the document
let document: PdfDocument = new PdfDocument(data);
// Gets the first page of the document
let page: PdfPage = document.getPage(0);
// Access the PDF form
let form: PdfForm = document.form;
// Create a new signature field
let field: PdfSignatureField = new PdfSignatureField(page, 'Signature', { x: 10, y: 10, width: 100, height: 50 });
// Define a callback function used for external signing
let externalSignatureCallback = (
    data: Uint8Array,
    options: {
        algorithm: DigestAlgorithm,
        cryptographicStandard: CryptographicStandard
    }
): { signedData: Uint8Array; timestampData?: Uint8Array } => {
    // Implement external signing logic here
    return new Uint8Array(); // Placeholder return
};
// Create a new signature using external signing with public certificate collection
let signature: PdfSignature = PdfSignature.create(
    externalSignatureCallback,
    publicCertificates,
    {
        cryptographicStandard: CryptographicStandard.cms,
        algorithm: DigestAlgorithm.sha256
    }
);
// Set the signature to the field
field.setSignature(signature);
// Add the field into PDF form
form.add(field);
// Save the document
document.save('output.pdf');
// Destroy the document
document.destroy();
// Load the document
var document = new ej.pdf.PdfDocument(data);
// Gets the first page of the document
var page = document.getPage(0);
// Access the PDF form
var form = document.form;
// Create a new signature field
var field = new ej.pdf.PdfSignatureField(page, 'Signature', { x: 10, y: 10, width: 100, height: 50 });
// Define a callback function used for external signing
var externalSignatureCallback = function (data, options) {
    // Implement external signing logic here
    return new Uint8Array(); // Placeholder return
};
// Create a new signature using external signing with public certificate collection
var signature = ej.pdf.PdfSignature.create(
    externalSignatureCallback,
    publicCertificates,
    {
        cryptographicStandard: ej.pdf.CryptographicStandard.cms,
        algorithm: ej.pdf.DigestAlgorithm.sha256
    }
);
// Set the signature to the field
field.setSignature(signature);
// Add the field into PDF form
form.add(field);
// Save the document
document.save('output.pdf');
// Destroy the document
document.destroy();

Retrieve the Signed Date of a PDF Signature

This example demonstrates how to retrieve the signed date of a PDF signature using the getSignedDate() method of the PdfSignature class. This property helps identify when the document was digitally signed.

TypeScript
JavaScript
import {PdfDocument, PdfPage, PdfForm, PdfSignatureField, DigestAlgorithm, CryptographicStandard} from '@syncfusion/ej2-pdf';

// Load the document
let document: PdfDocument = new PdfDocument(data);
// Get the first page of the document
let page: PdfPage = document.getPage(0);
// Access the PDF form
let form: PdfForm = document.form;
// Create a new signature field
let field: PdfSignatureField = new PdfSignatureField(page, 'Signature', { x: 10, y: 10, width: 100, height: 50 });
// Create a new signature using PFX data and private key
let sign: PdfSignature = PdfSignature.create(
    {
        cryptographicStandard: CryptographicStandard.cms,
        digestAlgorithm: DigestAlgorithm.sha256
    },
    certData,
    password
);
// Set the signature to the field
field.setSignature(sign);
// Get the signed date
sign.getSignedDate();
// Add the field into PDF form
form.add(field);
// Save the document
document.save('output.pdf');
// Destroy the document
document.destroy();
// Load the document
var document = new ej.pdf.PdfDocument(data);
// Get the first page of the document
var page = document.getPage(0);
// Access the PDF form
var form = document.form;
// Create a new signature field
var field = new ej.pdf.PdfSignatureField(page, 'Signature', { x: 10, y: 10, width: 100, height: 50 });
// Create a new signature using PFX data and private key
var sign = ej.pdf.PdfSignature.create({ cryptographicStandard: ej.pdf.CryptographicStandard.cms, digestAlgorithm: ej.pdf.DigestAlgorithm.sha256 }, certData, password);
// Set the signature to the field
field.setSignature(sign);
// Get the signed date
sign.getSignedDate();
// Add the field into PDF form
form.add(field);
// Save the document
document.save('output.pdf');
// Destroy the document
document.destroy();

Get Certificate Information from a PDF Signature

This example demonstrates how to retrieve the certificate information of a PDF signature using the getCertificateInformation() method of the PdfSignature class. This information includes details about the signer’s certificate used for digital signing.

TypeScript
JavaScript
import {PdfDocument, PdfPage, PdfForm, PdfSignatureField, DigestAlgorithm, PdfCertificateInformation, CryptographicStandard} from '@syncfusion/ej2-pdf';

// Load the document
let document: PdfDocument = new PdfDocument(data);
// Get the first page of the document
let page: PdfPage = document.getPage(0);
// Access the PDF form
let form: PdfForm = document.form;
// Create a new signature field
let field: PdfSignatureField = new PdfSignatureField(page, 'Signature', { x: 10, y: 10, width: 100, height: 50 });
// Create a new signature using PFX data and private key
let sign: PdfSignature = PdfSignature.create(
    {
        cryptographicStandard: CryptographicStandard.cms,
        digestAlgorithm: DigestAlgorithm.sha256
    },
    certData,
    password
);
// Set the signature to the field
field.setSignature(sign);
// Get the certificate information of the signature
let certificateInfo: PdfCertificateInformation = sign.getCertificateInformation();
// Add the field into PDF form
form.add(field);
// Save the document
document.save('output.pdf');
// Destroy the document
document.destroy();
// Load the document
var document = new ej.pdf.PdfDocument(data);
// Get the first page of the document
var page = document.getPage(0);
// Access the PDF form
var form = document.form;
// Create a new signature field
var field = new ej.pdf.PdfSignatureField(page, 'Signature', { x: 10, y: 10, width: 100, height: 50 });
// Create a new signature using PFX data and private key
var sign = ej.pdf.PdfSignature.create({ cryptographicStandard: ej.pdf.CryptographicStandard.cms, digestAlgorithm: ej.pdf.DigestAlgorithm.sha256 }, certData, password);
// Set the signature to the field
field.setSignature(sign);
// Get the certificate information of the signature
var certificateInfo = sign.getCertificateInformation();
// Add the field into PDF form
form.add(field);
// Save the document
document.save('output.pdf');
// Destroy the document
document.destroy();

Get Digital Signature Configuration Options

This example demonstrates how to retrieve the configuration options of a digital signature in a PDF document using the getSignatureOptions() method of the PdfSignature class. These options include details such as the cryptographic standard and digest algorithm used for signing.

TypeScript
JavaScript
import {PdfDocument, PdfPage, PdfForm, PdfSignature, PdfSignatureOptions, PdfSignatureField, CryptographicStandard} from '@syncfusion/ej2-pdf';

// Load the document
let document: PdfDocument = new PdfDocument(data);
// Get the first page of the document
let page: PdfPage = document.getPage(0);
// Access the PDF form
let form: PdfForm = document.form;
// Get the signature field
let field: PdfSignatureField = form.fieldAt(0) as PdfSignatureField;
// Get the PDF signature
let signature: PdfSignature = field.getSignature();
// Get the signature options
let options: PdfSignatureOptions = signature.getSignatureOptions();
// Get the cryptographic standard of the signature
let cryptographicStandard: CryptographicStandard = options.cryptographicStandard;
// Destroy the document
document.destroy();
// Load the document
var document = new ej.pdf.PdfDocument(data);
// Get the first page of the document
var page = document.getPage(0);
// Access the PDF form
var form = document.form;
// Get the signature field
var field = form.fieldAt(0);
// Get the PDF signature
var signature = field.getSignature();
// Get the signature options
var options = signature.getSignatureOptions();
// Get the cryptographic standard of the signature
var cryptographicStandard = options.cryptographicStandard;
// Destroy the document
document.destroy();

Replace Empty Signature with Externally Signed Data

This example demonstrates how to replace an empty signature field in a PDF document with externally signed data using the replaceEmptySignature() method of the PdfSignature class. This method allows embedding externally signed content, certificates, and optional timestamp data into the PDF.

TypeScript
JavaScript
import {PdfDocument, PdfPage, PdfForm, PdfSignatureField, DigestAlgorithm, CryptographicStandard} from '@syncfusion/ej2-pdf';

// Load the document
let document: PdfDocument = new PdfDocument(data);
// Get the first page of the document
let page: PdfPage = document.getPage(0);
// Access the PDF form
let form: PdfForm = document.form;
// Create a new signature field
let field: PdfSignatureField = new PdfSignatureField(page, 'Signature', { x: 10, y: 10, width: 100, height: 50 });
// Placeholder for signed data
let signedData: Uint8Array;
// Define a callback function used for external signing
let externalSignatureCallback = (
    data: Uint8Array,
    options: {
        algorithm: DigestAlgorithm;
        cryptographicStandard: CryptographicStandard;
    }
): void => {
    // Implement external signing logic here
    signedData = new Uint8Array(); // Placeholder return
};
// Create a new signature using external signing with public certificate collection
let signature: PdfSignature = PdfSignature.create(
    {
        cryptographicStandard: CryptographicStandard.cms,
        algorithm: DigestAlgorithm.sha256
    },
    externalSignatureCallback,
    publicCertificates
);
// Set the signature to the field
field.setSignature(signature);
// Add the field into PDF form
form.add(field);
// Save the document data
let data: Uint8Array = document.save();
// Destroy the document
document.destroy();
// Replace the empty signature with externally signed hash and certificates
let signedDocumentData: Uint8Array = PdfSignature.replaceEmptySignature(
    data,
    'Signature',
    signedData,
    DigestAlgorithm.sha256,
    publicCertificates
);
// Destroy the document
document.destroy();
// Load the document
var document = new ej.pdf.PdfDocument(data);
// Get the first page of the document
var page = document.getPage(0);
// Access the PDF form
var form = document.form;
// Create a new signature field
var field = new ej.pdf.PdfSignatureField(page, 'Signature', { x: 10, y: 10, width: 100, height: 50 });
// Placeholder for signed data
var signedData;
// Define a callback function used for external signing
var externalSignatureCallback = function (data, options) {
    // Implement external signing logic here
    signedData = new Uint8Array(); // Placeholder return
};
// Create a new signature using external signing with public certificate collection
var signature = ej.pdf.PdfSignature.create(
    {
        cryptographicStandard: ej.pdf.CryptographicStandard.cms,
        algorithm: ej.pdf.DigestAlgorithm.sha256
    },
    externalSignatureCallback,
    publicCertificates
);
// Set the signature to the field
field.setSignature(signature);
// Add the field into PDF form
form.add(field);
// Save the document data
var data = document.save();
// Destroy the document
document.destroy();
// Replace the empty signature with externally signed hash and certificates
var signedDocumentData = ej.pdf.PdfSignature.replaceEmptySignature(
    data,
    'Signature',
    signedData,
    ej.pdf.DigestAlgorithm.sha256,
    publicCertificates
);
// Destroy the document
document.destroy();

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