Is it possible to upgrade my license to allow more riders?
Yes, go into Analyzer's Help section and click on the Upgrade PerfPRO link. You also click on the upgrade link within Studio 2020's Dashboard Assignments section. The cost of an upgrade is roughly the difference between the two license prices.
From there follow through the steps within Analyzer. Once you get your new code you can then go back into the same Upgrade section and enter your new code. From there you should be good to go.
Contact support if you run into any issues.