For you math students out there you may realize that three years of app development on iOS means Readdle actually provided a document reader app before the App Store opened. Their apps are quite awesome, although they sometimes suffer from too many features (if simplicity is your thing). When we reviewed Scanner Pro, for example, the UI was a little overwhelming for TJ. Still, Readdle Docs is one of the best document viewers out there, and Flash Drive offers up some nice features like ZIP compression support. We reviewed BookReader here.
All of these apps (and more) are on sale for just $.99 until later today. For more info on the iPad giveaway, check Readdle's page here.