PureBasic

PDF Sign Unsigned Signature Field

See more PDF Signatures Examples

Demonstrates how to sign a PDF's unsigned signature field.

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

PureBasic

IncludeFile "CkCert.pb"
IncludeFile "CkJsonObject.pb"
IncludeFile "CkPdf.pb"

Procedure ChilkatExample()

    success.i = 0

    ; 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 containing an unsigned signature field.
    success = CkPdf::ckLoadFile(pdf,"qa_data/pdf/unsigned_sig_field/due_diligence.pdf")
    If success = 0
        Debug CkPdf::ckLastErrorText(pdf)
        CkPdf::ckDispose(pdf)
        ProcedureReturn
    EndIf

    ; 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.
    ; (image:https://example-code.com/images/unsignedSigField.jpg/endImage)

    ; 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)

    ; 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::ckUpdateBool(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::ckUpdateString(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::ckUpdateString(json,"appearance.text[0]","Digitally signed by: cert_cn")
    CkJsonObject::ckUpdateString(json,"appearance.text[1]","current_dt")
    CkJsonObject::ckUpdateString(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::ckUpdateString(json,"appearance.image","green-check-grey-circle")
    CkJsonObject::ckUpdateString(json,"appearance.imagePlacement","left")

    ; 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

    success = CkPdf::ckSignPdf(pdf,json,"qa_output/due_diligence_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."

    ; The appearance of the signature appears in Adobe Acrobat as shown below.
    ; (image:https://example-code.com/images/signature3.jpg/endImage)


    CkPdf::ckDispose(pdf)
    CkJsonObject::ckDispose(json)
    CkCert::ckDispose(cert)


    ProcedureReturn
EndProcedure