Many of you iOS users have most likely come across Readdle on the App Store at one point or another. If you haven’t, just know that they’re responsible for some of the best productivity apps on the iDevice. In fact, Calendars – Google Calendar client and PDF Expert for iPad are two apps I use on a daily basis. And seeing how it’s their 4th anniversary, Readdle have slashed 30% off on all their existing apps (sale good until end of today). Not only that, but they’re also giving away 4 iPad 2′s as well (3 left as contest officially started yesterday). More details on the giveaway and app links after the gap.