(Tcl) 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.

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load ./chilkat.dll

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

set pdf [new_CkPdf]

# Load a PDF to be signed.
# The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
set success [CkPdf_LoadFile $pdf "qa_data/pdf/hello.pdf"]
if {$success == 0} then {
    puts [CkPdf_lastErrorText $pdf]
    delete_CkPdf $pdf
    exit
}

# Options for signing are specified in JSON.
set json [new_CkJsonObject]

# In most cases, the signingCertificateV2 and signingTime attributes are required.
CkJsonObject_UpdateInt $json "signingCertificateV2" 1
CkJsonObject_UpdateInt $json "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.
CkJsonObject_UpdateInt $json "page" [CkPdf_get_NumPages $pdf]

# 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.
CkJsonObject_UpdateString $json "appearance.y" "bottom"
CkJsonObject_UpdateString $json "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.
CkJsonObject_UpdateString $json "appearance.fontScale" "9.0"

CkJsonObject_UpdateString $json "appearance.text[0]" "Digitally signed by: cert_cn"
CkJsonObject_UpdateString $json "appearance.text[1]" "current_dt"
CkJsonObject_UpdateString $json "appearance.image" "document-accepted"
CkJsonObject_UpdateString $json "appearance.imagePlacement" "left"
CkJsonObject_UpdateString $json "appearance.imageOpacity" "100"

# Load the signing certificate. (Use your own certificate.)
set cert [new_CkCert]

set success [CkCert_LoadPfxFile $cert "qa_data/pfx/myPdfSigningCert.pfx" "pfx_password"]
if {$success == 0} then {
    puts [CkCert_lastErrorText $cert]
    delete_CkPdf $pdf
    delete_CkJsonObject $json
    delete_CkCert $cert
    exit
}

# Tell the pdf object to use the certificate for signing.
set success [CkPdf_SetSigningCert $pdf $cert]
if {$success == 0} then {
    puts [CkPdf_lastErrorText $pdf]
    delete_CkPdf $pdf
    delete_CkJsonObject $json
    delete_CkCert $cert
    exit
}

set success [CkPdf_SignPdf $pdf $json "qa_output/hello_signed.pdf"]
if {$success == 0} then {
    puts [CkPdf_lastErrorText $pdf]
    delete_CkPdf $pdf
    delete_CkJsonObject $json
    delete_CkCert $cert
    exit
}

puts "The PDF has been successfully cryptographically signed."

# 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:

CkJsonObject_UpdateString $json "appearance.y" "792"
CkJsonObject_UpdateString $json "appearance.x" "0"

CkJsonObject_UpdateString $json "appearance.text[0]" "Digitally signed again by: cert_cn"
CkJsonObject_UpdateString $json "appearance.text[1]" "current_dt"
CkJsonObject_UpdateString $json "appearance.image" "document-accepted"
CkJsonObject_UpdateString $json "appearance.imagePlacement" "right"

set pdf2 [new_CkPdf]

set success [CkPdf_LoadFile $pdf2 "qa_output/hello_signed.pdf"]
set success [CkPdf_SetSigningCert $pdf2 $cert]

set success [CkPdf_SignPdf $pdf2 $json "qa_output/hello_signed2.pdf"]
if {$success == 0} then {
    puts [CkPdf_lastErrorText $pdf2]
    delete_CkPdf $pdf
    delete_CkJsonObject $json
    delete_CkCert $cert
    delete_CkPdf $pdf2
    exit
}

puts "The PDF has been successfully cryptographically signed again."

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


delete_CkPdf $pdf
delete_CkJsonObject $json
delete_CkCert $cert
delete_CkPdf $pdf2