@jfpo1991 Hi Jack, based on the types of changes you want to make here, I would suggest switching to a different theme. The main reason being that the PDF format can be quite brittle, especially if you have a lot of images and tables in your textbook. As you’ve also seen, changes in the PDF require more extensive customization, as compared to the webbook format. Generally, we suggest making as few CSS customizations as possible in all formats, as this may cause problems down the road, if not done correctly. Pressbooks’ themes are professionally designed with each format in mind, so the output is optimized, and hence the rules and structure of the stylesheets can vary by quite a bit. Transferring the customization you have in the Web stylesheet for PDF will need to be done manually, as you navigate through the different rules for the PDF stylesheet – unfortunately, there’s no easy way around this.
My suggestion to move forward for your book, looking at the changes in the webbook, would be to choose a different theme. I would recommend the McLuhan theme as it has a Serif heading and body font. If you did want the chapter titles to be centered along with a Serif font for headings and body, the Dillard theme might be one to consider (there is a setting in the Theme Options to remove the decorative glyph). Once you select a theme with the font and general layout that you are happy with, hopefully there won’t be too much else you would need to change.
I’m sorry if this wasn’t the answer that you were hoping for, but this will likely be the best path forward.