The copy will have the same targets as the spell or ability it's copying unless you choose new ones. You may change any number of the targets, including all of them or none of them. If the spell is a permanent spell with targets, such as an Aura, you may also choose a new target for that spell. The new targets must be legal. If, for any target, you can't choose a new legal target, then it remains unchanged (even if the current target is illegal).