The long awaited update of Pages 09, Pages 5.0, was released Oct. 22, 2013. It requires OS 10.9 Mavericks, and my initial testing indicates that there are substantial language improvements:
+Phonetic Guides for Chinese and Japanese (with the content suggested by the app itself)
+Ability to use Windows fonts (as well as Apple AAT) for Arabic and Indic scripts
+A direction control in the Format > Text menu for Right-to-Left text.
+Vastly improved cursor behavior for Arabic/Hebrew: It now follows the text from right to left and inserts text where you position it instead of somewhere else.
Someone who knows RTL scripts well will have to give it a thorough evaluation, but it looks like this app may finally be usable in this context.
One bug I have seen is that multicolumn layout does not work right.
Keynote and Numbers lack the text direction control found in Pages, but is seems some direction problems can be solved by a) running the app with the OS set to Arabic, or b) starting your composing with the keyboard set to US and then switching to Arabic when you actually need to input characters.
Support for certain Sanskrit conjuncts appears to be broken when using Apple's Devanagari fonts. Try Sanskrit 2003 instead.
Unfortunately vertical text for Chinese/Japanese is not yet available. Also my tests indicate Pages still cannot register the special Unicode characters ZWJ and ZWNJ required for certain Arabic and Indic scripts.
For Apple's info see
this.