(CkPython) PDF Sign Under Existing Signature

See more PDF Signatures Examples

This example explains how sign a previously-signed PDF and place the signature appearance below the existing signature.

Note: This example requires Chilkat v9.5.0.85 or greater.

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import sys
import chilkat

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

pdf = chilkat.CkPdf()

# Load a PDF to be signed.
success = pdf.LoadFile("qa_data/pdf/sign_testing_4/hello_signed.pdf")
if (success == False):
    print(pdf.lastErrorText())
    sys.exit()

# The PDF we'll be signing already has a signature added in Adobe Acrobat DC.
# It looks like this:
# (Notice the Adobe background logo, which is commonly what you'll see when a signature
# is created by Adobe Acrobat.  Chilkat (obviously) does not create signatures using the Adobe
# logo because it would be a copyright violation.)



# Options for signing are specified in JSON.
json = chilkat.CkJsonObject()

# In most cases, the signingCertificateV2 and signingTime attributes are required.
json.UpdateInt("signingCertificateV2",1)
json.UpdateInt("signingTime",1)

# To put our new signature underneath the existing signature, we have to specify the page
# where the existing signature is found, and then we can specify "under" for the "appearance.y"
json.UpdateInt("page",1)
json.UpdateString("appearance.y","under")

json.UpdateString("appearance.fontScale","10.0")

json.UpdateString("appearance.text[0]","Reason: Agreement Accepted by John")
json.UpdateString("appearance.text[1]","Date: current_dt")

# Load the signing certificate. (Use your own certificate.)
cert = chilkat.CkCert()
success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","secret")
if (success == False):
    print(cert.lastErrorText())
    sys.exit()

# Tell the pdf object to use the certificate for signing.
success = pdf.SetSigningCert(cert)
if (success == False):
    print(pdf.lastErrorText())
    sys.exit()

# Note: When adding an additional signature to a PDF, the existing signatures
# are validated, and this includes validating the certificates previously used to 
# create the existing signatures.  (A signature typically embeds the signing certs.)
# In some cases, the certificates and/or certs in the chain of authentication for 
# existing signatures are not present, and are not available on the current system.
# In this case, you can skip the validation by setting this keyword in UncommonOptions:
pdf.put_UncommonOptions("NO_VERIFY_CERT_SIGNATURES")

success = pdf.SignPdf(json,"qa_output/hello_signed.pdf")
if (success == False):
    print(pdf.lastErrorText())
    sys.exit()

print("The PDF has been successfully cryptographically signed.")

# Here's a screenshot of the 2nd signature positioned under the 1st in Adobe Acrobat: