I suspect you are using SuiteCRM 7.11.x? Let us know the version you are using as 7.12.x now has an updated PDF library.
IF it’s 7.11.x have a look at the documentation of mPDF here for adding Fonts. Fonts in mPDF 5.x – Fonts & Languages – mPDF Manual That SetAutoFonts I don’t believe it’s implying to be, but it detects the language of the input/characters to pick right font for that language i.e. german, chinese etc.
The config_fonts are in this directory in 7.11.x https://github.com/salesagility/SuiteCRM/tree/7.11.x/modules/AOS_PDF_Templates/PDF_Lib
How to make this upgrade safe I’m not quite sure, but it’s a starting point.