"Print to PDF" isn't clientside enough for you?
Anyway, if your operating system comes with a PDF printer or if you installed one manually, you can use the normal printing feature that every browser has.
Now matter how you look at it, it's not a feature that applications have to bother with reinventing.
My point is that not everyone has those features out of the box. Sure, you can install more software, but it's not a reason to not have a feature like that in this word processor.
Printing is the responsibility of the platform, not the application.
Something something Zawinski's Law.
https://developer.mozilla.org/en-US/docs/Web/API/Window/prin...