large PDF's freeze after I select text or i click on an area with no text

Adobe Acrobat Reader freeezes every time I highlight text. What I mean is that I left click, then drag my mouse to select text, after i let go of my left click button, the program freezes for like 10 seconds, then it shows the toolbar with options to highlight, cross-out, etc. 

It also freezes when I click on an area of the PDF where there is no text.

How do I fix this? thanks