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

add_filter("woe_formatter_pdf_use_external_font","__return_true");
add_filter("woe_formatter_pdf_apply_external_font",function($fpdf){
    $fpdf->setFontPath( dirname( __FILE__ ) ."/fonts/"); 
    $fpdf->AddFont( 'Code200365k', "", "Code200365k.ttf" );
    $fpdf->AddFont( 'Code200365k', "B", "Code200365k.ttf" );
    $fpdf->SetFont( 'Code200365k', '', 12 );
    return $fpdf;
});