(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.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Pdf, Cert, JsonObject;

...

procedure TForm1.Button1Click(Sender: TObject);
var
pdf: HCkPdf;
success: Boolean;
json: HCkJsonObject;
cert: HCkCert;

begin
// 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);

end;