The Help application on the Mac caches a lot of information to make help quicker. The down-side to this is that when you update an application, if you've looked at it recently in the Help application, your help for that application will probably be cached and you won't see any of the help topics that are specific to the new version.

If you find that your Help application is not finding things that you think it should, or it seems out of date, the easiest fix is to get rid of the cache. You can do this by closing the Help application and then opening the Finder. In your user home directory go to Library > Caches. You'll find directories called com.apple.helpdata, com.apple.helpui, and com.apple.helpviewer. Delete all of these directories and then restart the help application. It'll rebuild the caches and draw the new information from the application help files so everything will be current.