A great feature of Downloads is the file version capability it has. So you can have a file called Time Sheet and the first upload of that file is a blank file. Now your supervisor can download that version and make changes and upload a new version of that file which would contain the changes. They just make a note of the changes or something relevant in the change log.
So first browse to the file you want to upload a new version of and click on
Upload a new version
Next you click on
Click to Upload Files
Then you just have to fill in some
Change Log information (like maybe the date or a couple of words that explains the change)
Just click
Update Submission