(Node.js) PDF Sign Unsigned Signature Field

See more PDF Signatures Examples

Demonstrates how to sign a PDF's unsigned signature field.

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-node17-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node17-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node17-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node17-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node17-linux64');
    }
} else if (os.platform() == 'darwin') {
    var chilkat = require('@chilkat/ck-node17-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 containing an unsigned signature field.
    var success = pdf.LoadFile("qa_data/pdf/unsigned_sig_field/due_diligence.pdf");
    if (success == false) {
        console.log(pdf.LastErrorText);
        return;
    }

    // A PDF with an unsigned signature field appears in Adobe Acrobat as shown below.
    // (When the mouse pointer is hovered over the field, a tooltip will likely show a message
    // such as "Unsigned signature field (Click to sign)".  
    // This example code will automatically find the unsigned signature field,
    // and signs using your certificate.  It automatically sizes the text to the space alotted
    // for the signature.
    

    // 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);

    // We don't specify the page or a specific location because Chilkat will automatically
    // find the unsigned signature field and use its location and size and will scale the
    // signatures visual appearance (text + graphics) to the correct size required to fit.
    // We only need to indicate the desire to fill the unsigned signature field.
    json.UpdateBool("appearance.fillUnsignedSignatureField",true);

    // Starting in Chilkat v9.5.0.90, if a PDF contains multiple unsigned signature fields,
    // the field to be signed can be chosen by name:
    // To list unsigned signature fields, see this example: List PDF Unsigned Signature Fields
    json.UpdateString("unsignedSignatureField","doctor_signature");

    // Note: If the PDF document contains multiple unsigned signature fields, Chilkat will 
    // sign the 1st one found. 

    // In this example, the appearance of the digital signature will contain three lines:
    // 1) The signing certificate's common name
    // 2) The current date/time
    // 3) Some arbitrary text.
    // The keyword "cert_cn" is replaced with the Certificate's Subject Common Name.
    // The keyword "current_dt" is replaced with the current date/time.
    // Any number of appearance text lines can be added.
    json.UpdateString("appearance.text[0]","Digitally signed by: cert_cn");
    json.UpdateString("appearance.text[1]","current_dt");
    json.UpdateString("appearance.text[2]","The crazy brown fox jumps over the lazy dog.");

    // This signature will include one of the built-in SVG graphics (green-check-grey-circle).
    json.UpdateString("appearance.image","green-check-grey-circle");
    json.UpdateString("appearance.imagePlacement","left");

    // 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;
    }

    success = pdf.SignPdf(json,"qa_output/due_diligence_signed.pdf");
    if (success == false) {
        console.log(pdf.LastErrorText);
        return;
    }

    console.log("The PDF has been successfully cryptographically signed.");

    // The appearance of the signature appears in Adobe Acrobat as shown below.
    

}

chilkatExample();