Half a page sounds fair. If you feel compelled to write up to a page, go ahead. You need to say enough so that they remember you. At the same time, they arehave alot of essays to read and do not want to fall asleep reading a long winded personal statement.
Never assume in a personal statement that they have read your other essay. You need to actually state somewhere that entry to UOP will help you to achieve your goal of becoming a pharmacist. You don't have to go into detail on why you want to become a pharmacist if you don't want to. Just don't overlook an important point because it seems given.