wkhtmltopdf is broken and cannot render multiple fonts because of some issues around names. See wkhtmltopdf/wkhtmltopdf#2435
- Pick an 8 or less char name for each font and variation e.g. HelvBold, HelvLite, TimeReg
- Every variation needs to be a separate font file, with all the details renamed in Font Forge using the short name determined before.
- Give the font files the same short name (e.g. HelvBold.ttf)