Chinese characters into PDF attach mail error

Hi Tech support!

I get the issue, when finish booking, an email sent to my gmail with pdf attach file.
But the chinese text not show, it shows "?",
please see attach file and let me know if you have any ideas to fix it.

Thanks!
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Hello.
I have the same problem with the Russian font.
In what file you want to change the font?
Display the full path to the file.