(Perl) PDF Signature Page Location

See more PDF Signatures Examples

This example demonstrates how to specify the location of a PDF signature on a page.

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.
# The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
$success = $pdf->LoadFile("qa_data/pdf/hello.pdf");
if ($success == 0) {
    print $pdf->lastErrorText() . "\r\n";
    exit;
}

# 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);

# When cryptographically signing a PDF, the signature's appearance can be placed on a specific
# page in the PDF document, and at a specified location on the page.
# The 1st page of the PDF document is page number 1 (we don't use 0-based numbering for PDF page numbers).
# The PDF object has a NumPages property, so we can use it to sign on the last page of the PDF.
$json->UpdateInt("page",$pdf->get_NumPages());

# appearance.y and appearance.x JSON properties control the x,y location of the signature.
# The "appearance.y" can be "top" or "bottom".
# The "appearance.x" can be "left", "middle", or "right".
# It is also possible to specify exact PDF location in user space coordinates, which is discussed below.
$json->UpdateString("appearance.y","bottom");
$json->UpdateString("appearance.x","middle");

# In this example, the fontScale (in combination with the number of appearance text lines and the length of the longest text line),
# automatically determine the width/height of the signature text box. Any included graphic (JPG image or built-in SVG) is automatically
# scaled to fit. It is alternatively possible to specify the desired width/height of the signature rectangle.  In that case
# you would NOT specify a fontScale because Chilkat would automatically chose a font scale to fit the text to the desired rectangle.
# This example demonstrates how to specify the exact width/height of the PDF signature text box.
$json->UpdateString("appearance.fontScale","9.0");

$json->UpdateString("appearance.text[0]","Digitally signed by: cert_cn");
$json->UpdateString("appearance.text[1]","current_dt");
$json->UpdateString("appearance.image","document-accepted");
$json->UpdateString("appearance.imagePlacement","left");
$json->UpdateString("appearance.imageOpacity","100");

# Load the signing certificate. (Use your own certificate.)
$cert = chilkat::CkCert->new();
$success = $cert->LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","pfx_password");
if ($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/hello_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 here:

# ----------------------------------------------------------------------------------------------------
# *** Scroll down for information about specifying the PDF signature x,y location in user space coordinates.
# ----------------------------------------------------------------------------------------------------



# The x,y coordinates of a PDF page are in "user space", called "points", and there are 72 pointes per inch.
# A PDF page (8.5" x 11") is 612 points wide and 792 points high.
# The bottom left is at 0,0.    The top right is at 612,792.
# 
# To specify the location of a signature rectangle, the "appearance.y" is the y coordinate of the top of the signature rectangle,
# and the "appearance.x" is the x coordinate of the left of the signature rectangle.
# Therefore, to position the signature rectangle at the exact top/left of the page, we do this:

$json->UpdateString("appearance.y","792");
$json->UpdateString("appearance.x","0");

$json->UpdateString("appearance.text[0]","Digitally signed again by: cert_cn");
$json->UpdateString("appearance.text[1]","current_dt");
$json->UpdateString("appearance.image","document-accepted");
$json->UpdateString("appearance.imagePlacement","right");

$pdf2 = chilkat::CkPdf->new();
$success = $pdf2->LoadFile("qa_output/hello_signed.pdf");
$success = $pdf2->SetSigningCert($cert);

$success = $pdf2->SignPdf($json,"qa_output/hello_signed2.pdf");
if ($success == 0) {
    print $pdf2->lastErrorText() . "\r\n";
    exit;
}

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

# Here we have the PDF with the signature just added at the exact top/left.