Instead of the text displayed a question mark.

Hi m.a.emelyanov,

Please show some example.

original:
http://usedcont.com/kontejner-5-tonn-arkhangelsk.html?upm_export=pdf

P.S.: I used theme: Twenty Fifteen version 1.0

Ok, thank you.

I thought you've tried the option for Russian Language and it has not worked. But it seems you even don't know that there is such an option.

Please go to Dashboard > UPM Settings > Saving Manager
then scroll to PDF Save options Section, then find this option:

Extension for Documents in Russian Language
(If your blog is in Russian you should turn this extension on.
Если ваш блог на Русском языке, вы должны включить это расширение.)

Just turn it on, and all will be fine.

Yesss! Earned! Tom, Thank you very much for your help!!!!