How do I set a different font style than what is offered in the FontStyle enum?

I am creating PDF documents using SelectPdf. One of these documents needs to use a client-provided font.

The font family in question is Azo Sans, and it contains several different flavors of font such as bold, italic, regular, etc. It also contains styles like "thin". I need to use this thin style, coupled with italics, in my document.

How can I use a style that is not offered in the FontStyle enum?

I declare my font as such

var font = new Font(font: "Azo Sans", fontSize: 12, fontStyle: FontStyle.Italic | FontStyle.WhatStyleIsUsedHere?);

This works for standard styles like bold, underline, etc. How can I combine Italics with the Thin style offered by the Azo Sans font?