If you're already using DropBox, I think it offers tracking capabilities, so problem solved.
Although, if I had to solve this problem as specified, I'd upload multiple copies of the deck to my server and give each advisor a link to a separate copy. The server logs (or Google Analytics) will show when each file was accessed, and you'd know who it was because no one else knows about this particular link. But that may be too technical.
Of course, if all I wanted was to update my advisors, I'd just email them the deck as an attachment and ask them for receipt confirmation.