From Latest News Enhanced v3+
Upgrading from Latest News Enhanced v3+ to Latest News Enhanced Pro v3+ will enable all missing features of the commercial module. There is no loss of configuration. All instances of the free version will be transformed into instances of the full blown version.
The free module is automatically removed from the database in the process. The
modules/mod_latestnewsenhanced folder needs to be manually removed from the server directory.
From Latest News Enhanced v1.3.x to v2.5.x
There is no direct path to upgrade to Latest News Enhanced Pro. But, in order to avoid a complete re-configuration of the module instances created, the best solution is first to update the free module to its newest version (see the Updating older versions section), then to upgrade to the paid version.