papers vs written document

papers and written document both are nouns.

Word	Noun	Adjective	Verb	Adverb
papers	Yes	No	No	No
written document	Yes	No	No	No

As nouns, papers and written document are synonyms defined as:

papers and written document: writing that provides information (especially information of an official nature)

Other synonyms of papers include document.

papers (noun)	written document (noun)
writing that provides information (especially information of an official nature)	writing that provides information (especially information of an official nature)