Do you want Acrobat XI to be Arabic-enabled, with all the arabic-script features found in WinSoft International's Acrobat X ME?
Adobe have incorporated all those features in Acrobat XI, but you might have the devil's own job finding out how to access them (I know I did).
It's simple - no need to mess with your Windows Regional or keyboard settings - you need to download the "LS6" installer (same for InDesign, Illustrator and Photoshop CS6).
The LS6 installers are usually quoted as being for East European languages, but what's usually omitted is that the LS6 also includes "English (Arabic enabled)" (en_ae).
For Arabic enabled Acrobat XI, download the regular installer, and customize it with the free Adobe Customization Wizard XI tool.
In the "Installation Options" tab, under "Application Languages", select "English with Arabic support".
Make any other customizations you want, save package and run setup.exe (not AcroPro.msi) to install.
In Acrobat, you will find the ME features in Edit > Preferences > Language tab.