For Windows desktops and notebooks, Adobe Acrobat Reader is the most commonly used to read PDF files. This is because PDF is a proprietary format owned and patented by Adobe. Sometime in July 2008, Adobe released the PDF as an open public patent, granting rights to use, make, sell implementations of PDF. Lately, their very own Acrobat Reader has been upgraded to version 10 -- Acrobat Reader X as they call it. While it is the best version, it is plagued with its own set of headaches. To top this list is the freezing of the application when it opens a PDF file.
When you open a PDF file, Adober Acrobat Reader will launch and open the PDF file but it will sit there and freeze for about 15-20 seconds. The application window will display the "(Not Responding)" tag and once the window is focused the cursor becomes an hour glass. This is the manifestation of the freezing.
The freezing goes away after about 15-20 seconds and Acrobat Reader will function normally after that. This is true regardless of any PDF file opened. But the commonality of the problem seems to be related to version 10 (or X) of Adobe Acrobat Reader.
To resolve this issue, launch Acrobat Reader X. Under Edit -> Preferences -> General, untick the option "Enable Protected Mode at Startup" (refer to screenshot).
Accept all changes and re-launch Acrobat Reader or re-open that PDF file you were previously trying to view. Notice the big change in responsiveness. The freezing is gone.
Another suggestion in addition to this tweak is to remove files from %appdata%\Adobe\Acrobat. In this directory you will see versions of Acrobat Reader. Delete everything except "10.0". That also solved some problems with freezing along with the disabling of protected mode at startup. Hope this helps.
