Invoice wont show chars like š,č, ...

[lucas03]

Hi,
I've installed new prestashop RC2 and I'm playing with it. I viewed the invoice (its in slovak) and except chars like č and š and probably others is a question mark. So how could I fix it.

I've tried to google it, but havent found 100 percent solution that would be easy to integrate and would work on my version. I've read about replacing some codes (which Id like to avoid for compatibility reasons) and replacing fpdf with tcpdf.

I thought you might help better than testing all solutions I come across and then using backup if something goes wrong.

Thanks in advance.