affirm vs document

affirm is not a noun while document is a noun.

Word	Noun	Adjective	Verb	Adverb
affirm	No	No	Yes	No
document	Yes	No	Yes	No

As verbs, document is a hyponym of affirm; that is, document is a word with a more specific, narrower meaning than affirm:

Other hyponyms of affirm include back, back up, vouch, verify, demonstrate, establish, prove, shew, show, validate.

affirm (noun)	document (noun)
	anything serving as a representation of a person's thinking by means of symbolic marks
	writing that provides information (especially information of an official nature)
	(computer science) a computer file that contains text (and possibly formatting instructions) using seven-bit ASCII characters
	a written account of ownership or obligation

affirm (verb)	document (verb)
establish or strengthen as with new evidence or facts	support or supply with references
to declare or affirm solemnly and formally as true	record in detail
say yes to