I don’t export to PDF from Obsidian, so I am not in a good position to be able to help with a solution. The post linked below offers a way of styling a PDF with a css snippet. My assumption would be that you could use that snippet, changing the font to whatever you choose.
If it doesn’t work, hopefully someone else will be able to offer a solution.
EDIT: In a quick local test, the snippet below does work to change the font used in PDF exports.