In order to use Arabic fonts, you need to use special versions of InDesign, PhotoShop or Illustrator. These versions are labeled ME (Middle Eastern) and support bi-directional text setting for Arabic, Farsi and Hebrew. The regular version of Adobe CS3 doesnʼt support Arabic text setting.
Alternatively you can use ScribeDOOR plugin for Adobe CS, which adds the ability to edit and treat text in 21 complex languages, including Arabic, Hebrew, Farsi, Hindi, Urdu, Tamil and many scripts to create multilingual documents.
A cheaper, but more complicated alternative is to use World-ready composer.
On Mac OSX, Arabic will work at the system level in web browsers, in TextEdit and in the iWork suite (Pages, Keynote, Numbers). Mellel for OSX supports Arabic very well, and is a capable and affordable word processor.
It is expected that Adobe CS6 will support these languages without special plugins.