This might sound a bit awkward.

Let's imagine a black box computer, which doesn't accept any kind of input (except for keyboard/mouse), and it doesn't let you output anything but video signal (monitor). However it does let you print documents through an usb printer.

My question: is there any way to attach "whatever device" to the usb printer port so that it replaces the printer, but it's not a printer. Something that stores the printed documents in electronic format. I mean, can I make a "fake printer" using another PC, or a usb stick?

This is a quite general question, so I don't think more details are needed.

Thanks.