[XeTeX] Strange behaviour in PDF while using "Adobe Arabic Font"

[Jonathan Kew]

As has been explained previously (it should be in the list archives),  
this is a problem with OpenType/CFF fonts that are not designed with a  
1000-unit em-square, as is traditionally recommended for Type 1 fonts.  
The particular way in which they are embedded by xdvipdfmx (and  
apparently by LuaTeX, according to Khaled's report) is not properly  
handled by some readers.

My understanding is that the PDF specification is a little unclear  
about certain usage of a FontMatrix entry (sorry, don't have the exact  
details to hand now), so it may be debatable whether the PDF that  
xdvipdfmx is generating is correct or not. Note that older versions of  
Acrobat/Adobe Reader will display these PDFs correctly, however; it's  
only versions 8 and 9 that have problems with them.

If a PDF expert would like to examine and provide a patch for the font- 
embedding process in xdvipdfmx to make it more compatible, that would  
be great. The issue has been reported to Adobe, but I am not  
particularly hopeful they will modify their products to restore the  
previous behavior, although given the change that happened between  
versions 7 and 8, I think this can legitimately be called a regression  
on their part.

JK