I have found a better documentation about the format 2 for CMap of a TrueType font.
Here is the link : http://developer.apple.com/fonts/TTRefMan/RM06/Chap6cmap.html
In attachment you can find my implementation, however I didn't find font to test my code...
The patch include the patch of the
PDFBOX-668 task and a suggestion to send IOException instead of NullPointer during the parsing of TrueType Font if some tables are missing.