@BooDooInc
‘Distribute Form’ feature standalone AEM Designer 6.x is greyed out when the latest Acrobat DC is installed on the machine. If you have Acrobat 2017 then the feature is active and works as expected.
The issue is that the designer is not able to detect DC installation because of some discrepancy in the registry key with the latest DC installation.
This issue has been fixed with the latest AEM Forms 6.5/6.4 Designer software versions. AEM Forms 6.3 Designer is end of life so the fix to this issue hasn't been backported to 6.3.
Hope that helps!