Do online printable coupons actually work?

On Mommy Saves Big they have a bunch of really good printable coupons. I need coupons to Petco and Petsmart and they have a a bunch of great ones for the stores. Do the stores except these coupons though? They haven’t expired yet. These are NOT coupons for online stores, but coupons that you print out and physically take to a store.