PDF Generator unicode (Greek)

Hello,
i am creating a plugin, in which i want to generate simple pdf. I am trying to use dompdf, but i am experiencing problem with UNICODE characters (i am using Greek language).

Although, i have used all instructions from here, the characters are not generated, and i get empty boxes in place of the characters.

I have used the dejavy sans font-family with no luck. The problem remains

Has anyone used something else for pdf generation for unicode characters that work??

Thank you in advance