If the volume for your line of work is tens of thousands of pages, maybe printing 470 return slips is just y'know, fine, gets lost in the noise and makes everyone's life easier to just let it happen.
On the other hand, buying a $470 cake with your boss's money is no more efficient than paying yourself. It's "just" stealing.
Consider napkins at a fast food restaurant. Nobody would say you're "stealing" if you take one napkin and use it to clean your hands after eating. On the other hand, most people would call it "stealing" or at least ethically wrong if you took all the napkins that were available, far more than what you need. In this case, there's more to our ethical intuition than just "stealing" vs "not stealing". Factors include how much you need the napkins, how much you deprive others of the napkins, whether or not the restaurant would be ok with your behavior, whether or not the behavior is a cultural norm, etc.