> I hope one day Apple will create iWork with full Arabic support
Solving the problem is systemic: it involves the UCS/SFNT font model of the TrueType Specification that maps input characters to output glyphs, it involves mapping of layout rendering order to logical reading order in SGML-compatible DTD Document Type Definitions, and it involves modernised page description programming models.
Mac OS was the first system software to support Arabic in 1992. Apple's approach has the composition logic in the font file (like the successful ICC approach has the separation logic in the profile file). Microsoft's later approach has the layout logic in the application software, or in a system level layout shaper.
PostScript has no concept of Unicode page text, nor of the SFNT Spline Font file format required for complex rendering in Apple and Microsoft system software. PDF 1.5 and higher is able to embed the CMAP Character Map for simple TrueType shaping, if PostScript is not intermediate.
PDF 1.6 and higher is able to embed Microsoft extension tables (GPOS and GSUB) for reshaping, if PostScript is not intermediate. No version of the PDF Reference Manual has a specification for embedding Apple's extensions to the TrueType Specification. ISO 19005 PDF/A-1:2005 was not satisfactory for several reasons.
ISO 19005 PDF/A-2:2011 includes embedding of Unicode character information. This ISO upgrade is intended to compete with ECMA 388 Open XPS which Microsoft advertises has the ability to embed Unicode character information and SFNT Spline Font file format glyph runs (which is what produces WYSIWYS What You See Is What You Search for reshaping and reordering in complex line layout).
The root of all these problems is that the printing industry has rejected any and all page description programming models that solve the shortcomings in PostScript, since RIPs still process PDF by converting down to PostScript, so the RIPs that feed the printing presses become the real obstacle. The pressure to solve this problem somehow is big, but so is the problem.
The shortcomings of Arabic support in Pages have nothing at all to do with Postscript or PDF or anything else you mentioned.
They concern inappropriate cursor behavior, the lack of a setting for writing direction, and various other input system bugs. Apple long ago solved all of these problems in its TextEdit app. All it has to do is apply the same effort to Pages.