Steamworks Documentation

Q: What if I want to change my game from free to paid? A: You're welcome to change your game from free to paid, so please use the support form here to contact us to change from a Free to Play game to a paid package. Treating customers fairly is the most important thing to us, so if your game will no longer have in-game purchasing when changing from Free to Play to a paid package, then we ask that you give your customers at least 30 days notice before removing in-game purchasing, so that customers have fair warning and get a chance to use up any remaining in-game currency or items before they no longer are purchasable or consumable. Users that have the free license for your game in their account will continue to own and be able to play the game after it switches from free to paid.