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Signing a PDF Document with a SignatureWidget


Version Product Author
2024.1.124 RadPdfProcessing Desislava Yordanova


This article shows how to digitally sign an existing PDF document that already contains a SignatureField.

Unsigned PDF


Use the PdfFormatProvider to import the existing document and find the SignatureField to sign the document:

   PdfFormatProvider provider = new PdfFormatProvider();
   RadFixedDocument document = provider.Import(File.ReadAllBytes("Unsigned.pdf"));
   FormSource formSource = new FormSource();
   formSource.Size = new Size(420, 150);

   X509Certificate2 certificate = new X509Certificate2("Certificate.pfx", "Password");
   SignatureField signatureField = document.AcroForm.FormFields.Where(f => f.FieldType == FormFieldType.Signature).FirstOrDefault() as SignatureField;
   if (signatureField != null)
       signatureField.Signature = new Signature(certificate);
       SignatureWidget widget = signatureField.Widgets.FirstOrDefault();
       if (widget != null)
           formSource = widget.Content.NormalContentSource;
           FixedContentEditor ed = new FixedContentEditor(formSource);
           ed.TextProperties.FontSize = 60;
           ed.Position.Translate(30, 0);
           ed.DrawText("John Doe");
           ed.Position.Translate(0, 90);
           ed.TextProperties.FontSize = 20;
           ed.DrawText("Digitally signed on: " + DateTime.Now.ToString());
           ed.Position.Translate(40, 120);
           ed.TextProperties.FontSize = 20;
           ed.DrawText("(Click here to view the signature info)");


       string signedDocumentFilePath = "Signed.pdf";
       using (Stream output = new FileStream(signedDocumentFilePath, FileMode.OpenOrCreate, FileAccess.ReadWrite))
           provider.Export(document, output);

Signed PDF

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