Try use GNU FreeFont ( freeserif, freesans, freemono ) or "DejaVu fonts" instead "times" font and set the pdf printing to Latin Western Languages ( for this option you will change default font).
http://www.gnu.org/software/freefont/ranges/
http://dejavu-fonts.org/wiki/Main_Page
Download last tcpdf:
http://www.tcpdf.org/
It contains these fonts.
Unzip it into webERP/includes/tcpd/ folder.
Edit file:
webERP/includes/class.pdf.php
Find out these lines:
case 0:
$UserPdfFont = 'times';
break;
case 1:
$UserPdfFont = 'javierjp';
break;
case 2:
$UserPdfFont = 'javiergb';
break;
and change
$UserPdfFont = 'times';
to
$UserPdfFont = 'freeserif';
or to other fonts from webERP/includes/tcpdf/fonts/ folder.
I used freeserif: English, Arabic and Cyrillic in the same pdf are without problem.