stationery seller vs stationer

stationery seller and stationer both are nouns.

Word	Noun	Adjective	Verb	Adverb
stationery seller	Yes	No	No	No
stationer	Yes	No	No	No

As nouns, stationery seller and stationer are synonyms defined as:

stationery seller and stationer: a merchant who sells writing materials and office supplies

stationery seller (noun)	stationer (noun)
a merchant who sells writing materials and office supplies	a merchant who sells writing materials and office supplies