Jonathan Kehayias is going the opposite direction of the Jeffersons:
At some point in your career working with SQL Server, you will run into a situation where the wrong edition of SQL Server has been installed on a server and will need to change the edition for licensing reasons. Whether it is Enterprise Edition where Standard Edition should have been installed, Enterprise Edition where Developer Edition should have been used, or my favorite, Evaluation Edition where the 180 day trial has expired and Enterprise Edition isn’t going to be used, the only route available for downgrading the edition is to uninstall and reinstall SQL Server entirely. SQL Server Setup makes upgrading editions a piece of cake with SKUUPGRADE as a command line option for going from Standard/Developer/Evaluation to Enterprise, but anything else requires a full uninstall and reinstall to change the SKU/Edition and then restore all of the system and user databases to the new instance, which typically means a lot of work. I hate having to restore system databases and avoid having to do it if possible, so here is how I do this process and minimize the work required:
No matter what you are going to have to do an uninstall and reinstall of the SQL Server instance to downgrade the SKU. However, you can save yourself some time and the headache of trying to restore the system databases if you are careful about what you do. I have done a plenty of SKU downgrades in the past and the easiest way to do it, and I am not saying this is the Microsoft supported way but that it works if done correctly, is to:
Jonathan has an 11-point checklist that’s well worth checking out. Though hopefully, may all your editions be Enterprise…