There is currently no means to limit the number of times a document is uploaded, only a means to limit the maximum size for Attachments - the default is 25MB. We understand the need for this sort of feature and have created an Idea on our Community page to this effect. Please navigate to and log in or create an account. Once logged in, you may navigate to the Idea page below in order to comment and vote on the Idea:

Remember, the more votes an Idea receives, the more traction it will build with our Product Managers, so please encourage your colleagues to vote on the Idea as well!