I wanted to upgrade to the PRO version, but lost the upgrade link
Solution
Here's the link to the PRO version upgrade.
Keep in mind, that first, you need to have bought the basic version and have your basic account in good standing, in order for your PRO license to work.
The price of the PRO version is at least $89, but when someone pays for the basic version, we allow them to upgrade to PRO by paying the difference - and at a discounted rate.