(Perl) 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 Perl Downloads Perl Module for Windows, MacOS, Linux, Alpine Linux, Solaris

use chilkat();

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

$pdf = chilkat::CkPdf->new();

# Load a PDF to be signed.
$success = $pdf->LoadFile("qa_data/pdf/sign_testing_4/hello_signed.pdf");
if ($success == 0) {
    print $pdf->lastErrorText() . "\r\n";
    exit;
}

# 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 = chilkat::CkJsonObject->new();

# 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 = chilkat::CkCert->new();
$success = $cert->LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","secret");
if ($success == 0) {
    print $cert->lastErrorText() . "\r\n";
    exit;
}

# Tell the pdf object to use the certificate for signing.
$success = $pdf->SetSigningCert($cert);
if ($success == 0) {
    print $pdf->lastErrorText() . "\r\n";
    exit;
}

# 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->put_UncommonOptions("NO_VERIFY_CERT_SIGNATURES");

$success = $pdf->SignPdf($json,"qa_output/hello_signed.pdf");
if ($success == 0) {
    print $pdf->lastErrorText() . "\r\n";
    exit;
}

print "The PDF has been successfully cryptographically signed." . "\r\n";

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