PdfDocument pdf = new PdfDocument();
pdf.LoadFromFile(inputFile);
            PdfBookmarkCollection bookmarks = pdf.Bookmarks;
            for(int i = 0; i<bookmarks.Count; i++)
            {
                PdfBookmark bookmark = bookmarks[i];
SetBookmarkAction(bookmark);
            }
            pdf.SaveToFile(outputFile, FileFormat.PDF);

  private void SetBookmarkAction(PdfBookmark bookmark)
{
    PdfDestination dest = bookmark.Destination;
    dest.Mode = PdfDestinationMode.Location;
    dest.Zoom = 0;
    for (int i = 0; i < bookmark.Count; i++)
    {
        PdfBookmark childbookmark = bookmark[i];
        SetBookmarkAction(childbookmark);
    }
}

PdfDocument pdf = new PdfDocument();
pdf.LoadFromFile(inputFile);
            PdfAnnotationCollection annotations = pdf.Pages[0].AnnotationsWidget;
            for(int i = 0; i<annotations.Count; i++)
            {
                PdfDocumentLinkAnnotationWidget anno = annotations[i] as PdfDocumentLinkAnnotationWidget;
PdfDestination dest = anno.Destination;
dest.Mode = PdfDestinationMode.Location;
                dest.Zoom = 0;
                anno.Destination = dest;
            }
            pdf.SaveToFile(outputFile, FileFormat.PDF);
            pdf.Close();

static void Main(string[] args)
{

    PdfDocument doc = new PdfDocument();
    doc.LoadFromFile(@"test.pdf");
    PdfPageBase pagebase = doc.Pages[0];
    X509Certificate2 x509 = new X509Certificate2(@"gary.pfx", "e-iceblue");
    PdfOrdinarySignatureMaker signatureMaker = new PdfOrdinarySignatureMaker(doc, x509);
    IPdfSignatureAppearance signatureAppearance = new PdfCustomSignatureAppearance();
    signatureMaker.MakeSignature("Signature", signatureAppearance);
    doc.SaveToFile(@"new.pdf", Spire.Pdf.FileFormat.PDF);
    doc.Close();
}
public class PdfCustomSignatureAppearance : IPdfSignatureAppearance
{
    public void Generate(PdfCanvas g)
    {
        Image image = Image.FromFile("test.png");
        g.DrawImage(PdfImage.FromImage(image), new PointF(0, 0));
    }
}