I can't speak for FedEx: Office (Kinkos) , but I work as a Xerox Specialist at Office Depot (in the Copy and Print Department). We, the associates, have
no way of getting your card number. A manager can access the copier via the computer to retrieve a receipt if needed, but it only ends in the last four digits, as all receipts do. I'd also like to note that the managers cannot get your card number, either, due to the system that is used to protect against such things. When a card is swiped the information goes straight to credit processing, the information is not retained in the store or the register.
Despite popular belief, most of us retail people aren't out to get you
I am not sure why they would put large hard drives in a copy machines. The computers that operate the copiers do require space to run the operating system on the machine, as well as space to copy a
scanned (not copied) document to the network for retrieval.
I cannot speak for Xerox on the matter, but there isn't a feasible way to store every single copy ever done on the machine, but depending on the space of the hard disk in the machine, it could store quite a bit.