post-free vs post-paid

post-free is an adjective but post-paid is not an adjective.

Word	Noun	Adjective	Verb	Adverb
post-free	No	Yes	No	Yes
post-paid	No	No	No	Yes

As adverbs, post-free and post-paid are synonyms defined as:

post-free (adjective)	post-paid (adjective)
postpaid

post-free (adverb)	post-paid (adverb)
having the postage paid by the sender	having the postage paid by the sender