signatory vs attestor

signatory and attestor both are nouns.

Word	Noun	Adjective	Verb	Adverb
signatory	Yes	No	No	No
attestor	Yes	No	No	No

As nouns, attestor is a hyponym of signatory; that is, attestor is a word with a more specific, narrower meaning than signatory:

signatory: someone who signs and is bound by a document
attestor: (law) a person who attests to the genuineness of a document or signature by adding their own signature

Other hyponyms of signatory include cosignatory, cosigner, cosigner, abhorrer, endorser, indorser, attestant, attestator, witness.

signatory (noun)	attestor (noun)
someone who signs and is bound by a document	(law) a person who attests to the genuineness of a document or signature by adding their own signature