I have searched the archives for an answer to my problem that when I open a pdf in Acrobat Reader 8.0, my screen resolution setting goes from high res down to 1024x768. I have checked compatibility mode and I do not have that box checked on the Acrobat icon nor exe file. I read a thread that this was a known problem when opening the reader and that Adobe was working on a solution, but that thread was from 2013.
Is there a solution I have not found?
Why do you use this old version? Use Acrobat Reader DC.
If you are indeed using a 4K monitor, you are at least running on Windows 7 or later and in reality, only Windows 8.x and Windows 10 fully and properly support such monitors. Reader 8.0 was designed for Windows XP. And the first version of Adobe Reader (and Acrobat) to truly and properly support 4K monitors is Adobe Reader DC (and Acrobat DC).
As a free program, there is no good reason why you don't uninstall Adobe Reader 8.0 and then download, install, and use Adobe Reader DC which not only fully supports new hardware such as 4K monitors, touch screens, etc., but also is much more secure.