Delphi DLL

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.

Delphi DLL

var
success: Boolean;
pdf: HCkPdf;
json: HCkJsonObject;
cert: HCkCert;

begin
success := False;

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

pdf := CkPdf_Create();

//  Load a PDF to be signed.
success := CkPdf_LoadFile(pdf,'qa_data/pdf/sign_testing_4/hello_signed.pdf');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(pdf));
    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.)

//  

//  Options for signing are specified in JSON.
json := CkJsonObject_Create();

//  In most cases, the signingCertificateV2 and signingTime attributes are required.
CkJsonObject_UpdateInt(json,'signingCertificateV2',1);
CkJsonObject_UpdateInt(json,'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"
CkJsonObject_UpdateInt(json,'page',1);
CkJsonObject_UpdateString(json,'appearance.y','under');

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

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

//  Load the signing certificate. (Use your own certificate.)
cert := CkCert_Create();
success := CkCert_LoadPfxFile(cert,'qa_data/pfx/myPdfSigningCert.pfx','secret');
if (success = False) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

//  Tell the pdf object to use the certificate for signing.
success := CkPdf_SetSigningCert(pdf,cert);
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(pdf));
    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:
CkPdf_putUncommonOptions(pdf,'NO_VERIFY_CERT_SIGNATURES');

success := CkPdf_SignPdf(pdf,json,'qa_output/hello_signed.pdf');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(pdf));
    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:

//  

CkPdf_Dispose(pdf);
CkJsonObject_Dispose(json);
CkCert_Dispose(cert);