แก้ไขไฟล์ PDF ผ่าน C#

    Document doc = new Document(dataDir + "test.pdf");

    TextFragmentAbsorber textFragmentAbsorber = new TextFragmentAbsorber(searchTerm);
    TextSearchOptions textSearchOptions = new TextSearchOptions(true);
    textFragmentAbsorber.TextSearchOptions = textSearchOptions;

    doc.Pages.Accept(textFragmentAbsorber);
    TextFragmentCollection textFragmentCollection = textFragmentAbsorber.TextFragments;
    foreach (TextFragment textFragment in textFragmentCollection)
{
    Page page = textFragment.Page;
    Rectangle annotationRectangle = textFragment.Rectangle;
    
    Annotations.RedactionAnnotation annot = new Annotations.RedactionAnnotation(page, annotationRectangle);
    annot.FillColor = Color.Black;
    doc.Pages[textFragment.Page.Number].Annotations.Add(annot, true);
    annot.Redact();
}
    doc.Save(dataDir + "output.pdf");