If you have an older Pages version and you want to purchase the latest one at the Mac App Store, first you have to delete the old version. Open Finder, choose Applications in the sidebar and delete Pages.
Then, open the Mac App Store and purchase Pages. The most recent version will be installed, so you won't have to do anything after being installed. Also, you will be able to install Pages '09 as many times as you want in all your Macs for free
Thank you. This solved my problem. I actually already purchased 09 so I was able to redownload it after deleting 08.
Question though. I'm current at os 10.8.4. I noticed in my history of app purchases that all apps say "installed" except os Lion and os Snowlion, which have active download buttons. Is that just the way os is, it'll always say download instead of installed? Probably "stupid" question because I know my computer is up to date at 10.8.4.
Thanks for help on Pages.