Rust

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.

Rust

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

let pdf = chilkat::Pdf::new();

// Load a PDF containing an unsigned signature field.
if pdf.load_file("qa_data/pdf/unsigned_sig_field/due_diligence.pdf").is_err() {
    println!("{}", pdf.last_error_text());
    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.
// (image:https://example-code.com/images/unsignedSigField.jpg/endImage)

// Options for signing are specified in JSON.
let json = chilkat::JsonObject::new();

// In most cases, the signingCertificateV2 and signingTime attributes are required.
let _ = json.update_int("signingCertificateV2", 1);
let _ = json.update_int("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.
let _ = json.update_bool("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
let _ = json.update_string("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.
let _ = json.update_string("appearance.text[0]", "Digitally signed by: cert_cn");
let _ = json.update_string("appearance.text[1]", "current_dt");
let _ = json.update_string("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).
let _ = json.update_string("appearance.image", "green-check-grey-circle");
let _ = json.update_string("appearance.imagePlacement", "left");

// Load the signing certificate. (Use your own certificate.)
let cert = chilkat::Cert::new();
if cert.load_pfx_file("qa_data/pfx/myPdfSigningCert.pfx", "secret").is_err() {
    println!("{}", cert.last_error_text());
    return;
}

// Tell the pdf object to use the certificate for signing.
if pdf.set_signing_cert(&cert).is_err() {
    println!("{}", pdf.last_error_text());
    return;
}

if pdf.sign_pdf(&json, "qa_output/due_diligence_signed.pdf").is_err() {
    println!("{}", pdf.last_error_text());
    return;
}

println!("The PDF has been successfully cryptographically signed.");

// The appearance of the signature appears in Adobe Acrobat as shown below.
// (image:https://example-code.com/images/signature3.jpg/endImage)