How to add Custom Font
Go to Stores > Configuration > Sales > PDF Print-outs > Common Pdf Settings > Font and Barcode Settings > Upload Custom Font
Upload any true type font with a .ttf file extension. Once uploaded, save the configuration. You will then be able to select your font from the drop down box in the “Font” setting above this option.
If you don't see the option to upload the Custom font as shown in screenshot, please upgrade the PDF Customiser extension to at least version 8.0.5