CUPS didn’t work for me as I can’t see an upload option on the web UI.
CUPS is really intended as the backend. Whatever software you run will talk to CUPS.
I’ve never used it, but Savapage appears to be such a frontend.
EDIT: It may be more elaborate than what you want. It looks like this thing is capable of being set up to run a commercial printing service. It can probably also do what you want, but it’s going to have a lot of functionality that you wouldn’t use if you’re just running an unauthenticated, anyone-can-use-it system.