The Pro license unlocks the following capabilities that are not in the Lite version: Network Sync : Support for Google Calendar , Outlook (Windows only), and CalDAV/WebDAV servers. Import/Export : Ability to import and export data in CSV format for use in applications like Excel. Shared Task Lists : Synchronization of tasks between multiple devices. No Watermarks
Once you have your license.r2lic file, you can install it using several methods as discussed on the Rainlendar Forum : rainlendar pro license key