Swift

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.

Swift

func chilkatTest() {
    var success: Bool = false

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

    let pdf = CkoPdf()!

    // Load a PDF to be signed.
    success = pdf.loadFile(filePath: "qa_data/pdf/sign_testing_4/hello_signed.pdf")
    if success == false {
        print("\(pdf.lastErrorText!)")
        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.)

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

    // Options for signing are specified in JSON.
    let json = CkoJsonObject()!

    // In most cases, the signingCertificateV2 and signingTime attributes are required.
    json.updateInt(jsonPath: "signingCertificateV2", value: 1)
    json.updateInt(jsonPath: "signingTime", value: 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(jsonPath: "page", value: 1)
    json.updateString(jsonPath: "appearance.y", value: "under")

    json.updateString(jsonPath: "appearance.fontScale", value: "10.0")

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

    // Load the signing certificate. (Use your own certificate.)
    let cert = CkoCert()!
    success = cert.loadPfxFile(path: "qa_data/pfx/myPdfSigningCert.pfx", password: "secret")
    if success == false {
        print("\(cert.lastErrorText!)")
        return
    }

    // Tell the pdf object to use the certificate for signing.
    success = pdf.setSigningCert(cert: cert)
    if success == false {
        print("\(pdf.lastErrorText!)")
        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.uncommonOptions = "NO_VERIFY_CERT_SIGNATURES"

    success = pdf.sign(jsonOptions: json, outFilePath: "qa_output/hello_signed.pdf")
    if success == false {
        print("\(pdf.lastErrorText!)")
        return
    }

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

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

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

}