code: public byte[] getSignerContents() {
          if (PdfName.ADBE_X509_RSA_SHA1.equals(get(PdfName.SUBFILTER)))
              return pkcs.getEncodedPKCS1();
          else
              return pkcs.getEncodedPKCS7();
      }
docs: Gets the signature content. This can be a PKCS#1 or a PKCS#7. It corresponds to
  the /Contents key.
  @return the signature content