If you're upgrading to FeedDemon 4.0 from a previous version, please note that the setup program will install FeedDemon Lite, which is a free ad-supported version with a reduced feature set. Purchasing a serial number will convert FeedDemon Lite into FeedDemon Pro, which has the full feature set and doesn't show ads in the lower left corner.

More information about the differences between FeedDemon Lite and FeedDemon Pro may be found here.

Important: Before upgrading, it's recommended that you backup FeedDemon's cache folder (File > Manage Cache > Backup).