Apple discontinued sales and download of iWork '09 DVD and individual iWork '09 applications from the OS X app store in Fall 2013. None of the Apple links in your iWork '09 trialware are going to lead to converting your trialware to retail product. The trialware expired status has been set for this software.
Before you do the following, back-up any custom templates that you may have made to a folder in your home directory. The following location is where the individual iWork '09 application template folders live. Backup Pages, Numbers, and Keynote templates from the following location, by entering shift+command+G and copy/paste the following path into the dialog.
~/Library/Application Support/iWork/
However, because of the first paragraph, you will now need to remove all of the iWork '09 trialware prior to purchase and reinstallation of the retail DVD. Yvan Koenig, another volunteer in the Apple Support Community, has written an AppleScript that you run once, and it is configured to remove any iWork '09 application content. Nothing else. You can download the uninstall iWork '09.zip file, double-click it to unzip it, and then double-click the applescript file to load it into the Script Editor. You then click the hammer icon to compile it and click run. Then, you can do the following:
Spend $25 at Amazon, purchase the real iWork '09 DVD, and then, depending on the version of OS X that you have installed, you want to choose which mandatory Apple iWork '09 updater that you install.
Once you have the retail iWork '09 DVD installed, and the appropriate updater installed too, run Disk Utility and verify/repair your system file permissions.
