Do other file types do this? JPG, DOC, XLS, etc.
I ask because usually what you describe is a Windows Explorer issue, since the right click is fully a windows Graphical User Interface function, and until the Open with... and Reader is selected, the file isn't "handed off" to Adobe.
Usually when GIU functions slow down this way, it's either something tying up the processor, or a disk fragmentation slowing everything down.
Sometimes after a Microsoft Update, doc and xls files open slowly. Apparently, Microsoft Update keeps resetting the DDE (Dynamic Data Exchange) in the doc and xls file types. To fix this, I follow the instructions at the following Website:
Here are the instructions I follow for doc and xls.
If the problem is ONLY when you double-click on a file to open it. the
problem is likely due to DDE. It can be fixed by reinstalling, OR this
Go to Control Panel, Folder Options, File Types, scroll down to and
select XLS, click Advanced, select Open entry, click the edit Button.
Now uncheck "Use DDE" and then put your cursor in the Application box,
arrow all the way to the right and put in "%1" (include the quote
marks), IF there is /dde remove it. Then OK you way out. Things should
work quickly again.
After doing this, doc and xls files open normally again. But this does not work with pdf files, it has to be something else I haven’t figured out yet. The Disk Defragmanter Analysis says I don’t have to defrag my C: drive, and the system idle process is at 98% when the file is being opened.
If system idle is at 98% then it's definitely not a Reader issue. That means that ALL OTHER processes are only using 2% of your processor.
I still think it's something in your GUI causing Windows to "think" when you right click a pdf.