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.
I was being lazy in not testing it before I posted, and then I felt bad about potentially leaving the OP with half an answer and so thought I should give it a whirl. Worked perfectly, of course, in my local test … though we all have so many different setups and parameters that it might (I guess) work a little differently in another user’s vault.
Nice addition with the latest snippet. Will be useful for others. Appreciate the share.