Currently Being ModeratedFeb 8, 2013 1:54 PM (in response to chapster11)
How did you purchase the app? If you purchased a registration code to convert the trial version to a registered version, just re-enter it. If you purchased a DVD version, uninstall the Trial version and then reinstall from the DVD. Also if you plan to repurchase from the App Store, you will need to uninstall the Trial version. One of the helpers here, Yvan Koenig, wrote a script to do the uninstall operation. You can get the iWork 09 Uninstaller script here.
No matter what you do to get your app back, your documents are safe. They are not affected by the Uninstaller or by reinstallation of the apps.