How do you get rid of stuff in the purchased section of the App Store

Any items that aren't downloaded onto your iPad won't take up any space. Also you can't currently permanently delete any items from your purchase history, all you can do is hide them so that they are less visible : hiding and unhiding. If you are on iOS 6 on your iPad then you won't be able to hide them directly on it, but you should be able to hide them via your computer's iTunes.