ES4. The option the preview PDF (F5) is greyed out.

[#1]

I downloaded the trial for ES4 before purchasing it. I am using it with windows 8.1. The option the preview PDF (F5) is greyed out.

[#2]

I have Adobe Acrobat XI Pro and Adobe Reader DC installed.

[#3]

Do you have Adobe Acrobat installed? It is required for the preview capabilities.