Alongside OS X Mavericks, Apple also launched all-new iWork apps (Pages 5.0, Keynote 6.0 and Numbers 3.0) yesterday. If you can, you should update your old iWork apps for the benefit of much better iCloud and online collaboration with others and many more things.
For some users, those updates did not appear in the Mac App Store, even if they had bought the older iWork apps right there during the past couple of months.
Thankfully, there is an easy solution: just change your Mac’s system language to English and the updates should appear in the App Store.
To do that, go to System Preferences -> “Language & Region”, and make English your number one preferred language, then restart your Mac.