Control annotations visibility in PDF Viewer

11 Feb 20267 minutes to read

Overview

This guide shows how to display annotations in the Angular PDF Viewer while preventing them from appearing in the saved/downloaded PDF.

Steps to control annotation visibility

Step 1: Follow the steps in the getting-started guide (https://help.syncfusion.com/document-processing/pdf/pdf-viewer/angular/getting-started) to create a basic PDF Viewer sample.

Step 2: Add controls for annotation modification and downloading

Add buttons in the component template to modify annotations and to trigger a download of the PDF.

Standalone

import { Component, OnInit} from '@angular/core';
import {
  LinkAnnotationService,
  BookmarkViewService,
  MagnificationService,
  ThumbnailViewService,
  ToolbarService,
  NavigationService,
  AnnotationService,
  TextSearchService,
  TextSelectionService,
  FormFieldsService,
  FormDesignerService,
  PrintService,
  StickyNotesSettings,
  InkAnnotationSettings,
  HandWrittenSignatureSettings,
  DisplayMode,
  CustomStampSettings,
  StampSettings,
  StandardBusinessStampItem,
  SignStampItem,
  DynamicStampItem,
  FreeTextSettings,
  HighlightSettings,
  UnderlineSettings,
  StrikethroughSettings,
  LineSettings,
  ArrowSettings,
  RectangleSettings,
  CircleSettings,
  PolygonSettings,
  VolumeSettings,
  RadiusSettings,
  AreaSettings,
  PerimeterSettings,
  DistanceSettings,
  LoadEventArgs,
  PdfViewerComponent,

} from '@syncfusion/ej2-angular-pdfviewer';

// Import PdfAnnotationFlag and PdfDocument from the Syncfusion PDF library.
import { PdfAnnotationFlag, PdfDocument, PdfPage } from '@syncfusion/ej2-pdf';

@Component({
  selector: 'app-root',
  template: `
    <div class="content-wrapper">
      <button (click)="save()" style="margin-bottom: 20px;">Download</button>
      <ejs-pdfviewer
        id="pdfViewer"
        [documentPath]="document"
        [resourceUrl]="resourceUrl"
        (documentLoad)='documentLoaded($event)'
        style="height: 640px; display: block;">
      </ejs-pdfviewer>
    </div>
  `,
  providers: [
    LinkAnnotationService,
    BookmarkViewService,
    MagnificationService,
    ThumbnailViewService,
    ToolbarService,
    NavigationService,
    AnnotationService,
    TextSearchService,
    TextSelectionService,
    FormFieldsService,
    FormDesignerService,
    PrintService
  ]
})
export class AppComponent implements OnInit {
  public document: string = 'https://cdn.syncfusion.com/content/pdf/annotations-v1.pdf';
  public resourceUrl: string = 'https://cdn.syncfusion.com/ej2/28.1.33/dist/ej2-pdfviewer-lib';

  documentLoaded(e: LoadEventArgs): void {
    var viewer = (<any>document.getElementById('pdfViewer')).ej2_instances[0];

    //Code snippet to add basic annotations. You can also include other annotations as needed.
        viewer.annotation.addAnnotation("Highlight", {
            bounds: [{ x: 97, y: 610, width: 350, height: 14 }],
            pageNumber: 1
        } as HighlightSettings);
        viewer.annotation.addAnnotation("Underline", {
            bounds: [{ x: 97, y: 723, width: 353.5, height: 14 }],
            pageNumber: 1
        } as UnderlineSettings);
        viewer.annotation.addAnnotation("Strikethrough", {
            bounds: [{ x: 97, y: 836, width: 376.5, height: 14 }],
            pageNumber: 1
        } as StrikethroughSettings);
    }

ngOnInit(): void {

}
save() {
  // Get the PDF viewer instance from the DOM element
  var viewer = (<any>document.getElementById('pdfViewer')).ej2_instances[0];

  // Save the PDF document as a Blob
  viewer.saveAsBlob().then((blob: Blob) => {
    const reader = new FileReader();

    reader.onload = () => {
      // Convert Blob data to a Base64 encoded string
      let base64data = reader.result as string;

      // Extract the Base64 string from the Data URL
      const base64EncodedData = base64data.split('base64,')[1];

      // Create a PdfDocument instance with the Base64 data
      const document1 = new PdfDocument(base64EncodedData);

      // Iterate over each page and annotation to modify the annotation flags
      for (let i = 0; i < document1.pageCount; i++) {
        const page = document1.getPage(i);
        for (let j = 0; j < page.annotations.count; j++) {
          const annot = page.annotations.at(j);

          // Set the annotation flag to noView
          annot.flags |= PdfAnnotationFlag.noView;
        }
      }

      // Save the modified document as a Blob
      document1.saveAsBlob().then((modifiedBlob: { blobData: Blob }) => {
        const internalReader = new FileReader();

        internalReader.onload = () => {
          // Convert the modified Blob data to a Base64 encoded string
          const modifiedBase64 = internalReader.result as string;

          // Create a link to download the modified PDF
          const downloadLink = document.createElement('a');
          downloadLink.href = modifiedBase64;
          downloadLink.download = 'modified.pdf';
          downloadLink.click();
        };

        // Read the modified Blob data as a Data URL
        internalReader.readAsDataURL(modifiedBlob.blobData);
      });
    };

    // Read the original Blob data as a Data URL
    reader.readAsDataURL(blob);
  });
}
}

After performing these steps, annotations remain visible in the viewer but are hidden in the downloaded PDF.

View sample in GitHub