Perl Requires Chilkat v11.7.0+

Replace Text in a Signed PDF (PreserveSignatures)

See more PDF Text Replacement Examples

Applying a text replacement rewrites the page content, which invalidates any digital signature on the PDF. While the PreserveSignatures property is true (the default), "apply" is refused on a signed PDF; "check" only reads and is always allowed. Setting PreserveSignatures to false allows the replacement; the signature field stays in the written PDF but no longer verifies, so the document should be signed again afterwards if a signature is wanted. Chilkat2 Perl

use strict;
use warnings;
use Chilkat2;

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

# The PDF used in this example is available at invoice_signed.pdf

my $pdf = Chilkat2::Pdf->new;
my $success = $pdf->LoadFile('qa_data/pdf/invoice_signed.pdf');
if (!$success) {
    print $pdf->LastErrorText, "\n";
    exit;
}

print 'Signatures: ', $pdf->NumSignatures, "\n";

my $json = Chilkat2::JsonObject->new;
$json->UpdateString('labels[0].label', 'Invoice Number:');
$json->UpdateString('labels[0].value', 'INV-2026-0500');

# "check" reads only, so it works on a signed PDF.
my $jsonOut = Chilkat2::JsonObject->new;
$success = $pdf->TextReplace('check', $json, $jsonOut);
if (!$success) {
    print $pdf->LastErrorText, "\n";
    exit;
}

print 'check: ok = ', ($jsonOut->BoolOf('ok') ? 1 : 0), "\n";

# "apply" is refused while PreserveSignatures is true (the default).
$success = $pdf->TextReplace('apply', $json, $jsonOut);
if (!$success) {
    print 'apply refused: ', $pdf->LastErrorText, "\n";
}

# Allowing the signature to be broken:
$pdf->PreserveSignatures(0);
$success = $pdf->TextReplace('apply', $json, $jsonOut);
if (!$success) {
    print $pdf->LastErrorText, "\n";
    exit;
}

print 'applied: ', ($jsonOut->BoolOf('applied') ? 1 : 0), "\n";

# The written PDF is a full rewrite with the replacement.  The signature field is still in the document,
# but the bytes it signed are gone, so it no longer verifies.
$success = $pdf->WriteFile('qa_output/invoice_reissued_broken_signature.pdf');
if (!$success) {
    print $pdf->LastErrorText, "\n";
    exit;
}

print 'Signatures after writing: ', $pdf->NumSignatures, "\n";
my $sigInfo = Chilkat2::JsonObject->new;
my $validated = $pdf->VerifySignature(0, $sigInfo);
print 'Signature 0 verifies: ', ($validated ? 1 : 0), "\n";

# Sample output:

# Signatures: 1
# check: ok = true
# apply refused: ChilkatLog:
#   TextReplace:
#     DllDate: Nov  7 2026
#     ChilkatVersion: 11.7.0
#     UnlockPrefix: CHLKAT
#     UnlockStatus: 2
#     Architecture: Little Endian; 64-bit
#     Language: Visual C++ 11.0 / x64
#     VerboseLogging: 0
#     replaceTextOp:
#       op: apply
#       The PDF is signed: replacing text rewrites the content and invalidates the signatures (set PreserveSignatures = false to allow it).
#     --replaceTextOp
#     Failed.
#   --TextReplace
# --ChilkatLog
#
# applied: true
# Signatures after writing: 1
# Signature 0 verifies: false