The safe way is to prep the walls well first: clean them thoroughly with a damp cloth to get rid of dust and dirt, let them dry completely, and if the paint is really old or peeling in some spots, better not risk it there. Quality self-adhesive paper generally doesn't damage paint in good condition, but it all depends on how fragile the existing paint is - if paint comes off when you run your hand over it, that paper's going to be problematic. Ideally, test it in a corner or wall that's not too visible, wait a few days, and then try peeling it off carefully to see how it reacts; if the paint stays intact, go ahead with the rest of the apartment.