(PureBasic) 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.

Chilkat PureBasic Module Download Chilkat PureBasic Module

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.
    ; The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
    success.i = CkPdf::ckLoadFile(pdf,"qa_data/pdf/hello.pdf")
    If success = 0
        Debug CkPdf::ckLastErrorText(pdf)
        CkPdf::ckDispose(pdf)
        ProcedureReturn
    EndIf

    ; 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)

    ; 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::ckUpdateInt(json,"page",CkPdf::ckNumPages(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::ckUpdateString(json,"appearance.y","bottom")
    CkJsonObject::ckUpdateString(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::ckUpdateString(json,"appearance.fontScale","9.0")

    CkJsonObject::ckUpdateString(json,"appearance.text[0]","Digitally signed by: cert_cn")
    CkJsonObject::ckUpdateString(json,"appearance.text[1]","current_dt")
    CkJsonObject::ckUpdateString(json,"appearance.image","document-accepted")
    CkJsonObject::ckUpdateString(json,"appearance.imagePlacement","left")
    CkJsonObject::ckUpdateString(json,"appearance.imageOpacity","100")

    ; 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","pfx_password")
    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/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."

    ; 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::ckUpdateString(json,"appearance.y","792")
    CkJsonObject::ckUpdateString(json,"appearance.x","0")

    CkJsonObject::ckUpdateString(json,"appearance.text[0]","Digitally signed again by: cert_cn")
    CkJsonObject::ckUpdateString(json,"appearance.text[1]","current_dt")
    CkJsonObject::ckUpdateString(json,"appearance.image","document-accepted")
    CkJsonObject::ckUpdateString(json,"appearance.imagePlacement","right")

    pdf2.i = CkPdf::ckCreate()
    If pdf2.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkPdf::ckLoadFile(pdf2,"qa_output/hello_signed.pdf")
    success = CkPdf::ckSetSigningCert(pdf2,cert)

    success = CkPdf::ckSignPdf(pdf2,json,"qa_output/hello_signed2.pdf")
    If success = 0
        Debug CkPdf::ckLastErrorText(pdf2)
        CkPdf::ckDispose(pdf)
        CkJsonObject::ckDispose(json)
        CkCert::ckDispose(cert)
        CkPdf::ckDispose(pdf2)
        ProcedureReturn
    EndIf

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

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


    CkPdf::ckDispose(pdf)
    CkJsonObject::ckDispose(json)
    CkCert::ckDispose(cert)
    CkPdf::ckDispose(pdf2)


    ProcedureReturn
EndProcedure