As the description given above, it sounds like you are experiencing this problem on multiple computer?
Could you confirm the exact version of Adobe Reader installed on your users machine? Make sure that the application they are working on is up-to-date.
- Reboot the computer.
- Launch Acrobat Reader>Help>Check for update.
Let us know if it still doesn't help.
It is Adobe Acrobat Pro DC 2018 not Adobe Reader. Screen shot below
Sorry for the delay in response,
As you have confirmed it Acrobat DC, so did you also try to check the application's update? Or run the repair, Acrobat DC>Help>Repair Installation.
Unfortunately, we haven't received any screenshot in your previous response.