So I had an old version of iWork 09 lying around I purchased and have not used for years. I saw that Apple was offering free updates, but I have the rMBP without the CD drive. So I used my wife's MBP and installed it, but kept getting this error. I spent hours trying to figure this out as I really want to ditch Office for Mac 09. Here is what I did to get it to work. I found it on some comment where the person called Apple care.
Make sure iWork 09 is installed on your machine then do below:
Go to SYSTEM PREFERENCES --> USERS AND GROUPS -->
Unlock the little lock on the bottom right by clicking on it and then type in your password (you need to be on the admin account to do this)
Hit the little <PLUS> + sign on the bottom right
Create an account you will soon delete (I named mine 'test') and hit Create User
Then click on the newly created user on the list on the left
Check the box next to 'Allow user to administer this computer'
Then hit the little Apple logo and log out of current user
Log in to newly created user
Go update the new versions of Pages, Numbers, Keynote and sign in with your Apple account
I got a couple errors and it acted weird and had to restart the Mac App Store, but it worked
Log out of newly created user
Make sure all new Pages, Numbers, and Keynote are on your machine
Go back into Go to SYSTEM PREFERENCES --> USERS AND GROUPS -->
Click on the lock and log in
Hit the <Minus> - sign with the newly created account selected to delete the account
Choose option 'Delete the Home Folder'
Delete the old iWork 09 files
You should be good to go!
Hope this helps. It sure did for me. I know this is really basic, but I hate when people have instructions online and leave little things out and you can't follow them. Let me know if you have any other questions and enjoy the new applications. Thanks to Apple for being the best company in the world for allowing this update path. Goodby stupid Office for Mac 09. I'm off to download the new apps on my new iPhone 5s.
Thanks for reading,
Cody