From the help file, update before print. Looks like a hangover from slow machines and version minus 4 or something. If you had a lot of fields (like five or six), it used to slow the prog down immensely each time an update was required. So MS decided to allow you the option to turn off auto updates. However, if you printed, you would obviously want the updated info to print, so Word would update the fields. You might not even see the update in print preview, but on paper this would be fine.
On the Tools menu, click Options, and then click the Print tab.
Under Printing options, do one of the following:
To update fields, select the Update fields check box.
To update linked information, select the Update links check box.
One option is also to update fields manually. Can't remember where this is on the menu, but for sure if you right click on any field, the option to update is there.
Hope this helps.