You can allow students a variety of different file types and links. When you are creating an assignment you can choose for students upload files and/or links.
File types include: PDF (.pdf), Zip (.zip), Word (.doc/.docx), Excel (.xlsx), Sketch App (.sketch), iPython Notebook (.ipynb).
Any type of link can be uploaded including GoogleDocs and youtube. Be advised that GoogleDocs need to be uploaded as shared documents.
For both links and files, only one link or file can be uploaded per hand in.