(Perl) PDF Sign Unsigned Signature Field

See more PDF Signatures Examples

Demonstrates how to sign a PDF's unsigned signature field.

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 containing an unsigned signature field.
$success = $pdf->LoadFile("qa_data/pdf/unsigned_sig_field/due_diligence.pdf");
if ($success == 0) {
    print $pdf->lastErrorText() . "\r\n";
    exit;
}

# A PDF with an unsigned signature field appears in Adobe Acrobat as shown below.
# (When the mouse pointer is hovered over the field, a tooltip will likely show a message
# such as "Unsigned signature field (Click to sign)".  
# This example code will automatically find the unsigned signature field,
# and signs using your certificate.  It automatically sizes the text to the space alotted
# for the signature.


# 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);

# We don't specify the page or a specific location because Chilkat will automatically
# find the unsigned signature field and use its location and size and will scale the
# signatures visual appearance (text + graphics) to the correct size required to fit.
# We only need to indicate the desire to fill the unsigned signature field.
$json->UpdateBool("appearance.fillUnsignedSignatureField",1);

# Starting in Chilkat v9.5.0.90, if a PDF contains multiple unsigned signature fields,
# the field to be signed can be chosen by name:
# To list unsigned signature fields, see this example: List PDF Unsigned Signature Fields
$json->UpdateString("unsignedSignatureField","doctor_signature");

# Note: If the PDF document contains multiple unsigned signature fields, Chilkat will 
# sign the 1st one found. 

# In this example, the appearance of the digital signature will contain three lines:
# 1) The signing certificate's common name
# 2) The current date/time
# 3) Some arbitrary text.
# The keyword "cert_cn" is replaced with the Certificate's Subject Common Name.
# The keyword "current_dt" is replaced with the current date/time.
# Any number of appearance text lines can be added.
$json->UpdateString("appearance.text[0]","Digitally signed by: cert_cn");
$json->UpdateString("appearance.text[1]","current_dt");
$json->UpdateString("appearance.text[2]","The crazy brown fox jumps over the lazy dog.");

# This signature will include one of the built-in SVG graphics (green-check-grey-circle).
$json->UpdateString("appearance.image","green-check-grey-circle");
$json->UpdateString("appearance.imagePlacement","left");

# 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;
}

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

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

# The appearance of the signature appears in Adobe Acrobat as shown below.