1) Enable Arabic for Office. Start->All Programs->Microsoft
Office->Microsoft Office Tools->Microsoft Office 2007 Language Settings. On
the Enable tab, add Arabic as an Enabled language.
2) Boot Word. Click the Office button and Word Options from the bottom of
the menu. Switch to the Advanced tab, and scroll down a ways to the "Show
Document content" heading. Under it you should find a Numeral setting, where
you can choose Hindi. If you prefer to only show Hindi numerals for RTL
text, select Context.
If you write most or all of your documents in Arabic, I recommend setting
the default editing language to Arabic. In Step 1 above, there is a dropdown
at the bottom of the dialog to set this. That will make your documents in
Word RTL by default - RTL styles and RTL document view so you aren't manually
switching them.