C#

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.

C#

bool success = false;

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

Chilkat.Pdf pdf = new Chilkat.Pdf();

//  Load a PDF containing an unsigned signature field.
success = pdf.LoadFile("qa_data/pdf/unsigned_sig_field/due_diligence.pdf");
if (success == false) {
    Debug.WriteLine(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.
//  (image:https://example-code.com/images/unsignedSigField.jpg/endImage)

//  Options for signing are specified in JSON.
Chilkat.JsonObject 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.)
Chilkat.Cert cert = new Chilkat.Cert();
success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","secret");
if (success == false) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

//  Tell the pdf object to use the certificate for signing.
success = pdf.SetSigningCert(cert);
if (success == false) {
    Debug.WriteLine(pdf.LastErrorText);
    return;
}

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

Debug.WriteLine("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)