Does each form become encrypted or just the one that I click to encrypt

Hello, Jevans2015. If you are referring to the encryption forms, the moment you have enabled the option, the submissions that you will receive right after will be encrypted. Those submissions that were not encrypted will stay not being encrypted. 

Please note also that when you disable the option, the encrypted information will remain encrypted and will no longer be accessible, even if you still have the key with you. Re-enabling it will not work, and only the new data that comes after it will be decrypted by the new key. 

Feel free to check this guide to know more about encrypted forms: https://www.jotform.com/help/344-Encrypted-Forms-and-How-to-Use-Them