Sign a PDF document in Java

To sign an existing approval signature field in a PDF Document:

PDFDoc doc = new PDFDoc(docpath);

// Retrieve the unsigned approval signature field.
Field found_approval_field = doc.getField(approval_field_name);
DigitalSignatureField approval_digsig_field = new DigitalSignatureField(found_approval_field);

// (OPTIONAL) Add more information to the signature dictionary.
approval_digsig_field.setLocation("Vancouver, BC");
approval_digsig_field.setReason("Document approval.");
approval_digsig_field.setContactInfo("www.pdftron.com");

// (OPTIONAL) Add an appearance to the signature field.
Image img = Image.create(doc, appearance_img_path);
SignatureWidget approval_signature_widget = new SignatureWidget(found_approval_field.getSDFObj());
approval_signature_widget.createSignatureAppearance(img);

// Prepare the signature and signature handler for signing.
approval_digsig_field.signOnNextSave(private_key_file_path, keyfile_password);

// The actual approval signing will be done during the following incremental save operation.
doc.save(outpath, SDFDoc.SaveMode.INCREMENTAL, null);

Digitally sign PDF files
Full code sample which demonstrates using the digital signature API to digitally sign and/or certify PDF documents.

The Apryse SDK enables approval signatures in PDF documents using a Digital Certificate, in accordance with the latest PDF specification. By leveraging public key infrastructure (PKI) technology, with a certificate issued by a trusted certificate authority (CA), a signer can use a certificate-based digital ID to guarantee the authenticity of a signature. Placement of a digital signature using a certificate can also guarantee that a document was not modified since the signature was placed, ensuring the authenticity of the document.

Above is an example of a document containing a certified signature, guaranteed by a certificate generated by Apryse.com.