To add to what u/undetermined_outcom3 said, you can still print them but let them know the timeframe for getting them will take longer. You don't have to just come out and say "hey I can't afford that now" but can say something along the lines of "due to business constraints it may take a month or two to get the prints delivered, but let me know what you want printed and I will keep you updated when they come in and get shipped for delivery." That way it's still clear that you can't to it at the moment, but also still will honor the contract even a few years later.
And depending on what they want printed and at what size, it may not cost all that much anyway. So if you say that it may take a few months, and can then deliver within a month, that just makes it look like you're making even more of an effort than required by the contract.