Mac – way for registering iWork apps on App Store

Try the following steps in order:

1. Quit the App Store
2. Eject all disks (including any .dmg files you have mounted)
3. Use Spotlight to search your hard drive for anything with a similar name to your application.
4. If you find anything related to the application in question remove those files.
5. Delete the file at ~/Library/Preferences/com.apple.appstore.plist
6. Delete the file at ~/Library/Caches/com.apple.appstore/Cache.db
7. Delete the file at ~/Library/Cookies/com.apple.appstore.plist
8. Delete the file at ~/Library/Cookies/Cookies.plist
9. Open terminal and run this command: /System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -r -domain local -domain system -domain user
10. Logout of your computer & log back in
11. Reopen the Mac App Store
12. Try to install the application again.

Apple doesn't offer a way to move iWork licenses to the App Store. There isn't much to gain from such a move anyway because new major releases of iWork have (at least til now) always be sold as full versions only (which still was cheaper than e.g. MS Office upgrade versions).