I see empty boxes ([][][]) instead of symbols in PDF

Default font (used by PDF library) doesn’t support all UTF8 symbols.

So if you use Chinese, Arabic, Cyrillic, Hebrew  — you must install new font.

Please, use this way.

1. Download zip from https://freefontsdownload.net/free-st-gigafont-typefacescode2003-font-152444.htm

2. Run ftp client and create folder “fonts” inside active theme

3. Upload file Code200365k.ttf to folder “fonts”

4. Add following PHP code to functions.php