Word that describes what will be a collection of a particular type of document

You can try dossier defined by Merriam Webster as

 A group of papers that contain detailed information about someone or some thing.

File containing detailed records on a particular person or subject.

Not a single-word name, but if it’s a sub-file of a file whose name already includes “Applications,” you could call it “Supporting Documentation,” which this About Careers article describes in paragraph 2 as including:
“a resume, a cover letter, transcripts, writing samples, Veterans' Preference documents, portfolios, certifications, a reference list, letters of recommendation, and other supporting documentation as specified in the job posting.”

If it’s a stand-alone file (or maybe even if it isn’t), you should probably add a third word, i.e., “Applicant’s” (or Applicants’ if it includes documents from more than one applicant): “Applicant’s/Applicants’ Supporting Documentation”