The fonts for this theme are a little scattered and I did not do them properly…but for the most part, you can do a custom css as:
You can make it whatever percent you want, but default is usually 100% or you can go more. This will affect other sizes throughout your pages, but there are some areas where they won’t be affected. Those ones you will need to add css to size them up manually. One of the reasons why relative sizing works best compared to px sizes (fixed sizing).
A little update on Preference….the plan is to actually rebuild it from the ground up and bring it up to date with better code, features, and fixing things like the font issues. My new theme Circumference has some font management added.