Pascal (Lazarus/Delphi)

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.

Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.Pdf,
  Chilkat.Cert,
  Chilkat.JsonObject;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  pdf: TPdf;
  json: TJsonObject;
  cert: TCert;

begin
  success := False;

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

  pdf := TPdf.Create;

  //  Load a PDF to be signed.
  success := pdf.LoadFile('qa_data/pdf/sign_testing_4/hello_signed.pdf');
  if (success = False) then
    begin
      WriteLn(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:https://example-code.com/images/signed_once_with_adobe_acrobat.jpg/endImage)

  //  Options for signing are specified in JSON.
  json := TJsonObject.Create;

  //  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 := TCert.Create;
  success := cert.LoadPfxFile('qa_data/pfx/myPdfSigningCert.pfx','secret');
  if (success = False) then
    begin
      WriteLn(cert.LastErrorText);
      Exit;
    end;

  //  Tell the pdf object to use the certificate for signing.
  success := pdf.SetSigningCert(cert);
  if (success = False) then
    begin
      WriteLn(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,'qa_output/hello_signed.pdf');
  if (success = False) then
    begin
      WriteLn(pdf.LastErrorText);
      Exit;
    end;

  WriteLn('The PDF has been successfully cryptographically signed.');

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

  //  (image:https://example-code.com/images/signed_under_existing_signature.jpg/endImage)


  pdf.Free;
  json.Free;
  cert.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.