Acrobat Reader's slow speed. You can speed up acrobat reader easily by doing this.
Go to the installation folder of acrobat reader. I mean where you installed your software. It usually likes -
C:\program files\adobe\acrobat\reader\ if you install it in your C:/ drive.
Move all the files and folders from the "plugins" directory to the "Optional" directory.
Don't copy just Cut. Make sure that acrobat is not opened.
Now see the magic.
Off-topic but one thing I want to say that If you search for good PDF reader, I can recommend
"PDFXchangeViewer" . It is small in size. But do more work than Adobe.Its size is considerably small too than adobe.