some characters don't seem in pdf

[slayer35]

>Hi,Some of turkish characters is missing in the pdf.
>I'm converting gridview to pdf by doing the same way as this article says (http://hamang.net/2008/08/14/html-to-pdf-in-net/).But some of characters are missing in pdf.
>I search a lot but can't find any solution.
>Any help will be appreciated
>thanks.