Non-US character support?

Greetings

I’m using WP 3.5.1.
recently I installed this plugin and got PDF file which is filled in question mark, not characters.
I assume it is related in Asian font (especially Korean), but have no way to diagnose.

please take care of this issue, if possible 🙂

Thanks and happy WPing.

http://wordpress.org/extend/plugins/post-pdf-export/