async function main() {
  const doc = await PDFNet.PDFDoc.createFromFilePath(in_docpath);

  // Retrieve the unsigned approval signature field.
  const found_approval_field = await doc.getField(in_approval_field_name);
  const found_approval_signature_digsig_field = await PDFNet.DigitalSignatureField.createFromField(found_approval_field);

  // (OPTIONAL) Add more information to the signature dictionary.
  await found_approval_signature_digsig_field.setLocation('Vancouver, BC');
  await found_approval_signature_digsig_field.setReason('Document certification.');
  await found_approval_signature_digsig_field.setContactInfo('www.pdftron.com');

  // (OPTIONAL) Add an appearance to the signature field.
  const img = await PDFNet.Image.createFromFile(doc, in_appearance_img_path);
  const found_approval_signature_widget = await PDFNet.SignatureWidget.createFromObj(await found_approval_field.getSDFObj());
  await found_approval_signature_widget.createSignatureAppearance(img);

  // Prepare the signature and signature handler for signing.
  await found_approval_signature_digsig_field.signOnNextSave(in_private_key_file_path, in_keyfile_password);

  // The actual approval signing will be done during the following incremental save operation.
  await doc.save(in_outpath, PDFNet.SDFDoc.SaveOptions.e_incremental);
}
PDFNet.runWithCleanup(main);