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(PureBasic) PDF Sign Under Existing Signature
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.
IncludeFile "CkCert.pb"
IncludeFile "CkJsonObject.pb"
IncludeFile "CkPdf.pb"
Procedure ChilkatExample()
; This example requires the Chilkat API to have been previously unlocked.
; See Global Unlock Sample for sample code.
pdf.i = CkPdf::ckCreate()
If pdf.i = 0
Debug "Failed to create object."
ProcedureReturn
EndIf
; Load a PDF to be signed.
success.i = CkPdf::ckLoadFile(pdf,"qa_data/pdf/sign_testing_4/hello_signed.pdf")
If success = 0
Debug CkPdf::ckLastErrorText(pdf)
CkPdf::ckDispose(pdf)
ProcedureReturn
EndIf
; 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.i = CkJsonObject::ckCreate()
If json.i = 0
Debug "Failed to create object."
ProcedureReturn
EndIf
; In most cases, the signingCertificateV2 and signingTime attributes are required.
CkJsonObject::ckUpdateInt(json,"signingCertificateV2",1)
CkJsonObject::ckUpdateInt(json,"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"
CkJsonObject::ckUpdateInt(json,"page",1)
CkJsonObject::ckUpdateString(json,"appearance.y","under")
CkJsonObject::ckUpdateString(json,"appearance.fontScale","10.0")
CkJsonObject::ckUpdateString(json,"appearance.text[0]","Reason: Agreement Accepted by John")
CkJsonObject::ckUpdateString(json,"appearance.text[1]","Date: current_dt")
; Load the signing certificate. (Use your own certificate.)
cert.i = CkCert::ckCreate()
If cert.i = 0
Debug "Failed to create object."
ProcedureReturn
EndIf
success = CkCert::ckLoadPfxFile(cert,"qa_data/pfx/myPdfSigningCert.pfx","secret")
If success = 0
Debug CkCert::ckLastErrorText(cert)
CkPdf::ckDispose(pdf)
CkJsonObject::ckDispose(json)
CkCert::ckDispose(cert)
ProcedureReturn
EndIf
; Tell the pdf object to use the certificate for signing.
success = CkPdf::ckSetSigningCert(pdf,cert)
If success = 0
Debug CkPdf::ckLastErrorText(pdf)
CkPdf::ckDispose(pdf)
CkJsonObject::ckDispose(json)
CkCert::ckDispose(cert)
ProcedureReturn
EndIf
; 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:
CkPdf::setCkUncommonOptions(pdf, "NO_VERIFY_CERT_SIGNATURES")
success = CkPdf::ckSignPdf(pdf,json,"qa_output/hello_signed.pdf")
If success = 0
Debug CkPdf::ckLastErrorText(pdf)
CkPdf::ckDispose(pdf)
CkJsonObject::ckDispose(json)
CkCert::ckDispose(cert)
ProcedureReturn
EndIf
Debug "The PDF has been successfully cryptographically signed."
; Here's a screenshot of the 2nd signature positioned under the 1st in Adobe Acrobat:
CkPdf::ckDispose(pdf)
CkJsonObject::ckDispose(json)
CkCert::ckDispose(cert)
ProcedureReturn
EndProcedure
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