theoretically vs on paper

theoretically and on paper both are adverbs.

Word	Noun	Adjective	Verb	Adverb
theoretically	No	No	No	Yes
on paper	No	No	No	Yes

As adverbs, theoretically and on paper are synonyms defined as:

theoretically (adverb)	on paper (adverb)
in theory; according to the assumed facts	as written or printed
in a theoretical manner	in theory; according to the assumed facts