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How To Create and Modify Links (Link Annotations) In A PDF Document

One of our customers wrote: “I want to inspect each link annotation, find out its type and destination and edit only those annotations pointing to a remote document.”
By Santhanam L.

In this article, you will learn how to create and edit actions for PDF link annotations. Action elements specify what happens when a user clicks on a link annotation in a PDF file.

There are several types of PDF actions - go-to, remote go-to, URI, JavaScript, launch, and named.

For this article, I will limit myself to go-to and remote go-to actions. A go-to action links to a destination in the same document while a remote go-to action links to a destination in another PDF document.

Our customer had a PDF document containing several link annotations. In particular, some link annotations had remote go-to actions - all of which were set to destinations in another PDF document.

A problem arose when the second PDF document was moved to a different location and all the remote go-to actions of link annotations in the original PDF document needed to be updated with the new path of the second document.

To reproduce the problem, let us create a PDF document (C:\Old_Path\document1.pdf) with two link annotations. A go-to action will be associated with the first link annotation and a remote go-to action will be associated with the second link annotation. The remote go-to action will be linked to a destination in another PDF document (C:\Old_Path\document2.pdf).

void createLinkAnnotActions() throws IOException, PdfException {
  // Create a new PDF document
  PdfDocument doc1 = new PdfDocument();
   
  // Create font instances
  PdfFont fontHelvetica = 
    PdfFont.create("Helvetica",
                   15,
                   PdfEncodings.WINANSI);
                   fontHelvetica.setColor(Color.blue);
  PdfFont fontHelveticaSmall = 
    PdfFont.create("Helvetica",
                   10,
                   PdfEncodings.WINANSI);
                   fontHelveticaSmall.setColor(Color.black);

  // Create new page 1
  PdfPage tempPage1 = new PdfPage(PdfPageSize.A4);

  // Write text on page 1 using the fonts
  tempPage1.writeText(
    "Create and Modify PDF Annotation Actions",
    fontHelvetica,
    PdfTextFormatter.LEFT,
    50, 50);
  tempPage1.writeText(
    "Link to page 2 of this document.",
    fontHelveticaSmall,
    50, 100);
  tempPage1.writeText(
    "Link to page 3 of remote document.",
    fontHelveticaSmall,
    50, 120);

  // Create link annotation 1 on the first text element
  PdfLinkAnnot linkAnnot1 = 
    new PdfLinkAnnot(new PdfRect(81, 100, 33, 14),
                     Color.white);
  linkAnnot1.setHighlightMode(PdfLinkAnnot.HIGHLIGHT_MODE_INVERT);
  // Add a go-to action to link annotation 1
  linkAnnot1.addAction(new PdfGotoAction(2, 0, 0, 100));

  // Create link annotation 2 on the second text element
  PdfLinkAnnot linkAnnot2 =
    new PdfLinkAnnot(new PdfRect(81, 120, 33, 14),
                     Color.white);
  linkAnnot2.setHighlightMode(PdfLinkAnnot.HIGHLIGHT_MODE_INVERT);
  // Add a remote go-to action to link annotation 2
  linkAnnot2.addAction(
    new PdfRemoteGotoAction("C:\\Old_Path\\document2.pdf", 3, true));

  // Add the link annotations to page 1
  tempPage1.addAnnotation(linkAnnot1);
  tempPage1.addAnnotation(linkAnnot2);

  // Add page 1 to document
  doc1.add(tempPage1);    

  // Create page 2
  tempPage1 = new PdfPage(PdfPageSize.A4);
  // Write some text on page 2
  tempPage1.writeText("Page 2", 50, 50);
  // Add page 2 to the document
  doc1.add(tempPage1);

  // Save document to file
  doc1.save("document1.pdf");
  doc1.close();
}

Now, we assume that document2.pdf was moved from C:\Old_Path to D:\New_Path and update remote go-to actions for the link annotations in document1.pdf accordingly.

For this, we first load document1.pdf, retrieve its first page, iterate through all link annotations in that page, get all actions for each link annotation that is found, and update any remote go-to action with the new location of document2.pdf.

void manageLinkAnnotActions() throws IOException, PdfException {
   
  // Load document in which links need to be modified
  PdfDocument doc2 = new PdfDocument();
  doc2.load("document1.pdf");
   
  String sExistingPath = "C:\\Old_Path";
  String sReplacementPath = "D:\\New_Path";
   
  // Access page 1
  PdfPage tempPage2 = doc2.getPage(1);
   
  // Obtain all link annotations in the page 
  List annotsList = tempPage2.getAllAnnotations(PdfAnnot.ANNOT_TYPE_LINK);
   
  // Iterate through the obtained annotations
  for (int i = 0, n = annotsList.size(); i < n; i++) {
    PdfLinkAnnot linkAnnot = (PdfLinkAnnot) annotsList.get(i);
     
    // Retrieve all remote go-to actions of 
    // the current link annotation
    List actionsList = linkAnnot.getAllActions(PdfAction.REMOTE_GOTO);
     
    // Iterate through the remote go-to 
    // actions of the current link annotation
    for (int j = 0, o = actionsList.size(); j < o; j++) {
      PdfRemoteGotoAction remoteGoToAction
         = (PdfRemoteGotoAction) actionsList.get(j);

      // Check for old pathname in the file pathname 
      // of the remote go-to action
      if (remoteGoToAction.getPdfFilePath().startsWith(sExistingPath)) {
        // Replace old pathname with new pathname
        remoteGoToAction.setPdfFilePath(
        remoteGoToAction.getPdfFilePath().replaceAll(
          "C:\\\\Old_Path",  // regex
          sReplacementPath));
      }        
    }
  }
   
  // Save modified document to file     
  doc2.save("document1_modified.pdf");
  doc2.close();
}

We use the getAllAnnotations() method of the page object to retrieve all link annotations objects in the page. We then call getAllActions() of each annotation and get a list of remote go-to action objects. The getPdfFilePath() is used to retrieve old pathname of document2.pdf. Finally, we use setPdfFilePath() to update the remote go-to action with the new pathname of document2.pdf.

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