(Tcl) PDF Sign Unsigned Signature Field

See more PDF Signatures Examples

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 containing an unsigned signature field.
set success [CkPdf_LoadFile $pdf "qa_data/pdf/unsigned_sig_field/due_diligence.pdf"]
if {$success == 0} then {
    puts [CkPdf_lastErrorText $pdf]
    delete_CkPdf $pdf
    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.
set json [new_CkJsonObject]

# In most cases, the signingCertificateV2 and signingTime attributes are required.
CkJsonObject_UpdateInt $json "signingCertificateV2" 1
CkJsonObject_UpdateInt $json "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.
CkJsonObject_UpdateBool $json "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
CkJsonObject_UpdateString $json "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.
CkJsonObject_UpdateString $json "appearance.text[0]" "Digitally signed by: cert_cn"
CkJsonObject_UpdateString $json "appearance.text[1]" "current_dt"
CkJsonObject_UpdateString $json "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).
CkJsonObject_UpdateString $json "appearance.image" "green-check-grey-circle"
CkJsonObject_UpdateString $json "appearance.imagePlacement" "left"

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

set success [CkCert_LoadPfxFile $cert "qa_data/pfx/myPdfSigningCert.pfx" "secret"]
if {$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 $json "qa_output/due_diligence_signed.pdf"]
if {$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 below.


delete_CkPdf $pdf
delete_CkJsonObject $json
delete_CkCert $cert