undocumented vs unregistered

undocumented and unregistered both are adjectives.

Word	Noun	Adjective	Verb	Adverb
undocumented	No	Yes	No	No
unregistered	No	Yes	No	No

undocumented (adjective)	unregistered (adjective)
lacking necessary documents (as for e.g. permission to live or work in a country)	not registered
	(of animals) not recorded with or certified by an official breed association
	(a boat or vessel) not furnished with official documents