You can upgrade your Woostify Pro license at any point through your Woostify account. When upgrading, you will only need to pay for the difference between your current license and the one you are upgrading to.
How to upgrade?
1. Go to https://woostify.com/my-account/ and log in your account
2. Click Purchase History tab
3. Select View license that you want to upgrade
4. Select View Upgrade and choose plan to Upgrade
5. Click Purchase and add the billing detail