Because the card-draw ability is granted to the creature, if an opponent takes control of the enchanted creature and it deals combat damage while they control it, that opponent will draw a card.
Enchant creature
Enchanted creature has "Whenever this creature deals combat damage to a player, draw a card."
As long as enchanted creature is legendary, it gets +1/+1 and has ward . (Whenever enchanted creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays .)
. (Whenever enchanted creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays