From my sandbox test, signing a signature field with Aspose places the following text into the signature field:
Digitally Signed by “CN=xyz, OU=abc, OU=pki…”
Date: yyyy-mm-dd…
I am looking to be able to customize the …...Digital Signature, customize "sign by" text Aspose.PDF Product...into the signature field: Digitally Signed by “CN=xyz, OU=abc...