You can use ctrl + alt + tab to jump between all opened process windows.
Documents in Reader open up as separate window and thus Ctrl+Tab, which basically switches between different tabs, wouldn't work. Instead you can use the Alt+Tab or Win+Tab to switch between different windows.
LALT + TAB should help.
I am working all the time with many programs opened and Alt+Tab is worse because I have to go between the opened programs and the opened PDF documents.
Adobe, please bring back Ctrl+Tab.
I think that the correct answer is: Downgrade. Use v7.