C#

PDF Signature with Background Image (Seal/Stamp/etc.)

See more PDF Signatures Examples

Demonstrates how to sign a PDF with an appearance that includes a background image, such as a seal, stamp, etc.

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 to be signed.
//  The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
success = pdf.LoadFile("qa_data/pdf/hello.pdf");
if (success == false) {
    Debug.WriteLine(pdf.LastErrorText);
    return;
}

//  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);

//  Put the signature on page 1, top left
json.UpdateInt("page",1);
json.UpdateString("appearance.y","top");
json.UpdateString("appearance.x","left");

//  Use a font scale of 10.0
json.UpdateString("appearance.fontScale","10.0");

//  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.");

//  Load a JPG image to be shown with 30% opacity in the background.
//  (the image must be in the JPG format)
//  The sample university.jpb is available at https://example-code.com/images/university.jpg

Chilkat.BinData jpgData = new Chilkat.BinData();
success = jpgData.LoadFile("qa_data/jpg/university.jpg");
if (success == false) {
    Debug.WriteLine("Failed to load the JPG image.");
    return;
}

success = pdf.SetSignatureJpeg(jpgData);
if (success == false) {
    Debug.WriteLine(pdf.LastErrorText);
    return;
}

//  Specify that we want to display the JPG image in the center with 30% opacity.
json.UpdateString("appearance.image","custom-jpg");
json.UpdateString("appearance.imagePlacement","center");
json.UpdateString("appearance.imageOpacity","30");

//  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/hello_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.
//  The JPG is automatically scaled to the size of the signature based on the signature's font scale
//  and number of text lines.
//  (image:https://example-code.com/images/signature2.jpg/endImage)