Since Redax is compatible under all versions of Windows, what matters more is the version of Acrobat you are running.
Redax 5.6 is compatible under Acrobat 8, 9, 10 & 11.
Redax 5.7 is compatible under Acrobat DC only.
Redax 5.8 is compatible under Acrobat DC, 2017 and 2020.
If you need to upgrade your version of Redax, please contact sales@appligent.com.