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Delphi ActiveX

PDF Sign Under Existing Signature

See more PDF Signatures Examples

This example explains how sign a previously-signed PDF and place the signature appearance below the existing signature.

Note: This example requires Chilkat v9.5.0.85 or greater.

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var
success: Integer;
pdf: TChilkatPdf;
json: TChilkatJsonObject;
cert: TChilkatCert;

begin
success := 0;

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

pdf := TChilkatPdf.Create(Self);

//  Load a PDF to be signed.
success := pdf.LoadFile('qa_data/pdf/sign_testing_4/hello_signed.pdf');
if (success = 0) then
  begin
    Memo1.Lines.Add(pdf.LastErrorText);
    Exit;
  end;

//  The PDF we'll be signing already has a signature added in Adobe Acrobat DC.
//  It looks like this:
//  (Notice the Adobe background logo, which is commonly what you'll see when a signature
//  is created by Adobe Acrobat.  Chilkat (obviously) does not create signatures using the Adobe
//  logo because it would be a copyright violation.)

//  image

//  Options for signing are specified in JSON.
json := TChilkatJsonObject.Create(Self);

//  In most cases, the signingCertificateV2 and signingTime attributes are required.
json.UpdateInt('signingCertificateV2',1);
json.UpdateInt('signingTime',1);

//  To put our new signature underneath the existing signature, we have to specify the page
//  where the existing signature is found, and then we can specify "under" for the "appearance.y"
json.UpdateInt('page',1);
json.UpdateString('appearance.y','under');

json.UpdateString('appearance.fontScale','10.0');

json.UpdateString('appearance.text[0]','Reason: Agreement Accepted by John');
json.UpdateString('appearance.text[1]','Date: current_dt');

//  Load the signing certificate. (Use your own certificate.)
cert := TChilkatCert.Create(Self);
success := cert.LoadPfxFile('qa_data/pfx/myPdfSigningCert.pfx','secret');
if (success = 0) then
  begin
    Memo1.Lines.Add(cert.LastErrorText);
    Exit;
  end;

//  Tell the pdf object to use the certificate for signing.
success := pdf.SetSigningCert(cert.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(pdf.LastErrorText);
    Exit;
  end;

//  Note: When adding an additional signature to a PDF, the existing signatures
//  are validated, and this includes validating the certificates previously used to 
//  create the existing signatures.  (A signature typically embeds the signing certs.)
//  In some cases, the certificates and/or certs in the chain of authentication for 
//  existing signatures are not present, and are not available on the current system.
//  In this case, you can skip the validation by setting this keyword in UncommonOptions:
pdf.UncommonOptions := 'NO_VERIFY_CERT_SIGNATURES';

success := pdf.SignPdf(json.ControlInterface,'qa_output/hello_signed.pdf');
if (success = 0) then
  begin
    Memo1.Lines.Add(pdf.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('The PDF has been successfully cryptographically signed.');

//  Here's a screenshot of the 2nd signature positioned under the 1st in Adobe Acrobat:

//  image