Acrobat becomes very slow when I open large PDF files (200+ pages).

@James_Anderson5352  try this first... and maybe the Acrobat Preferences isn't the issue.... 

DO you have the 'New Acrobat' Interface on or off? If you go to View is it: 

• Enable new Acrobat (it's off)
• Disable new Acrobat (it's on)

If 'it's on' I would turn it off. It It will automatically restart Acrobat. It has been noted that many who work with large, complex, or heavily annotated documents—report that this new interface has a detrimental impact on performance and responsiveness. Test this if it works... if not...

In Acrobat Preferences (Command K for the MAC, or Control K for the PC), under Page Display, uncheck the following in Rendering: Use Page Cache; Smooth text, Smooth line art, Smooth images

as well under 3D & Multimedia change the Preferred Rendered to the Software — We are trying to speed up the rendering.

You could even re-save the same PDF under a different name, and Compress the PDF - Advanced Optimization to a lower resolution! 

*NOTE: Some people will suggest change and uncheck the security preferences, which can also bog the PDF down—but I normally don't because for me it's all about safety and security to my computer and documents