Node.js

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.

Node.js

NODEJS_PRELUDE

function chilkatExample() {

    var success = false;

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

    var pdf = new chilkat.Pdf();

    //  Load a PDF to be signed.
    success = pdf.LoadFile("qa_data/pdf/sign_testing_4/hello_signed.pdf");
    if (success == false) {
        console.log(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.
    var json = new chilkat.JsonObject();

    //  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.)
    var cert = new chilkat.Cert();
    success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","secret");
    if (success == false) {
        console.log(cert.LastErrorText);
        return;
    }

    //  Tell the pdf object to use the certificate for signing.
    success = pdf.SetSigningCert(cert);
    if (success == false) {
        console.log(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.SignPdf(json,"qa_output/hello_signed.pdf");
    if (success == false) {
        console.log(pdf.LastErrorText);
        return;
    }

    console.log("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)

}

chilkatExample();