(Go) PDF Sign Under Existing Signature

See more PDF Signatures Examples

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

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

    pdf := chilkat.NewPdf()

    // Load a PDF to be signed.
    success := pdf.LoadFile("qa_data/pdf/sign_testing_4/hello_signed.pdf")
    if success == false {
        fmt.Println(pdf.LastErrorText())
        pdf.DisposePdf()
        return
    }

    // 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.NewJsonObject()

    // 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.NewCert()
    success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","secret")
    if success == false {
        fmt.Println(cert.LastErrorText())
        pdf.DisposePdf()
        json.DisposeJsonObject()
        cert.DisposeCert()
        return
    }

    // Tell the pdf object to use the certificate for signing.
    success = pdf.SetSigningCert(cert)
    if success == false {
        fmt.Println(pdf.LastErrorText())
        pdf.DisposePdf()
        json.DisposeJsonObject()
        cert.DisposeCert()
        return
    }

    // 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.SetUncommonOptions("NO_VERIFY_CERT_SIGNATURES")

    success = pdf.SignPdf(json,"qa_output/hello_signed.pdf")
    if success == false {
        fmt.Println(pdf.LastErrorText())
        pdf.DisposePdf()
        json.DisposeJsonObject()
        cert.DisposeCert()
        return
    }

    fmt.Println("The PDF has been successfully cryptographically signed.")

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

    

    pdf.DisposePdf()
    json.DisposeJsonObject()
    cert.DisposeCert()