paid vs gainful

paid and gainful both are adjectives.

Word	Noun	Adjective	Verb	Adverb
paid	No	Yes	No	No
gainful	No	Yes	No	No

As adjectives, paid and gainful are synonyms defined as:

Other synonyms of paid include paying.

paid (adjective)	gainful (adjective)
marked by the reception of pay	yielding a fair profit
involving gainful employment in something often done as a hobby
yielding a fair profit