You aren't doing anything wrong. The problem is in some coding Apple has not fixed & probably never will. This means that at some time you had the iWork ’09 trial installed. You need to delete the trial & then reinstall from the boxed DVD or the Mac App Store. The files to delete are the iWork ’09 folder from the main HD > Applications; the iWork ’09 folder in HD > Library > Application Support & the individual iWork application plist files found in HD > Users > (your account) > Library > Preferences for each user. Yvan Koenig has written an AppleScript that removes the files. You can find it on his box.com account in for_iWork'09 > other_iWork'09 items > uninstall iWork '09.zip.