PDFsharp & MigraDoc Forum

private void FixLinks(PdfDocument doc2_, PagePairs pp_, int iPageOffset_)
{
  int iPageCount = pp_.GetSize();
  for (int j = 0; j < iPageCount; j++)
  {
    PdfPage? page1 = null;
    PdfPage? page2 = null;
    pp_.GetPagePair(j, out page1, out page2);
    if ((page1 == null) || (page2 == null))
      return;

    List<PdfAnnotation> la2Remove = new();
    List<PdfAnnotation> la2Add = new();
    // Go through the annotations of the original page in PDF2
    for (int i = 0; i < page2.Annotations.Count; i++)
    {
      PdfAnnotation annot = page2.Annotations[i];
      if (annot.Elements.GetString(PdfAnnotation.Keys.Subtype) != "/Link")
        continue; // Not a link

      PdfArray? dest = annot.Elements.GetArray("/Dest");
      if (dest == null)
        continue; // Link without destination?

      PdfRectangle rect = annot.Elements.GetRectangle(PdfAnnotation.Keys.Rect);
      int i0basePageIndex2 = -1;
      PdfReference? targetPage = dest.Elements.GetReference(0);
      if (targetPage == null)
      { // This is a document link that points to a specific page with a 0-based index
        try
        {
          i0basePageIndex2 = dest.Elements.GetInteger(0);
        }
        catch (InvalidCastException)
        {
          continue;
        }
      }
      else
      { // This is a link that points to a specific location on a page.
        // Try to find the referenced page in PDF2
        for (int p = 0; p < doc2_.PageCount; p++)
        {
          if (doc2_.Pages[p].Reference == targetPage)
          { // This is the page that was referenced in PDF2. Remember the 0-based index
            i0basePageIndex2 = p;
            break;
          }
        }
      }
      if (i0basePageIndex2 > -1)
      { // Remember which annotation that was imported into PDF1 to remove
        la2Remove.Add(page1.Annotations[i]);
        // Then create a new annotation to add later
        la2Add.Add(PdfLinkAnnotation.CreateDocumentLink(rect, i0basePageIndex2 + 1 + iPageOffset_));
      }
    }
    // Remove the annotation to replace
    foreach (PdfAnnotation a in la2Remove)
      page1.Annotations.Remove(a);

    // Then add the new one
    foreach (PdfAnnotation a in la2Add)
      page1.Annotations.Add(a);
  }
}