There is no way of hiding these on iPad as suggested.
There is no way of hiding the purchased apps on iPad as suggested. There is no "hide" button as suggested. I have tried and it does not have a button.
iMovie '11, Mac OS X (10.7.4)
If you have iOS 6 on your iPad then it won't work - from the page that you posted from :
You currently cannot hide purchases on devices using iOS 6.
You should still be able to do it on your Mac's iTunes, which will hide it from the Purchased link uder Quicklinks on your Mac's iTunes and from the Purchased tab on your iPad