When sending a document for approval and while publishing a document, there will be a check box for receipt report, selecting the check box will give you a notification when the document has been viewed by the members.

Adding a comment to the document: You can post a comment on the document by typing in the Comment field.

Type of documents can I add to my project
Any Drawing, Picture, Invoice, RFC, RFI or any other type of file can be added from your computer.