The signature field's /T name.
The signer name (/Name), or null.
The stated reason (/Reason), or null.
The stated location (/Location), or null.
The signing date string (/M, e.g. D:20260624…), or null.
The /SubFilter (e.g. adbe.pkcs7.detached), or null.
The /ByteRange [a, b, c, d] the signature covers.
One signature on the document (a
/Sigfield's/V), from GigaPdfDoc.signatures.