(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.

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOSX, and ARM

var os = require('os');
if (os.platform() == 'win32') {  
    if (os.arch() == 'ia32') {
        var chilkat = require('@chilkat/ck-node11-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node11-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node11-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node11-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node11-linux64');
    }
} else if (os.platform() == 'darwin') {
    var chilkat = require('@chilkat/ck-node11-macosx');
}

function chilkatExample() {

    // 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.
    var 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.)

    

    // 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:

    

}

chilkatExample();