The following procedure will introduce how to upgrade your plan, like changing your current monthly plan to an annually plan. If you wish to downgrade your current plan, saying annually to monthly subscription, you will need to cancel your current active subscription, let it expire until the end of your contract, and then purchase the monthly plan.
1. Inside Foxit application, go to Help menu, click on Manage.
2. Click on Manage Your Subscription(Personal).
3. Click on Change under the plan which you want to switch current plan to.
4. Follow the on-screen tips to finish the change.