Word isn't bundled by default but you can print anything to PDF. Windows ships with a PDF printer installed, so you could print from Notepad to PDF if you'd like.
PDF readers haven't been required for over 10 years? Chrome shipped with a PDF viewer eons ago and of course the old version of Edge and current Chromium Edge (and now Firefox, as of a week or two ago) have PDF viewers.
macOS Preview is limited to PDF 1.4. That kind of sucks. Not a deal breaker for most PDFs, but I've come across one or two that won't render and I had to figure out why.
Yes. When you type "word" in the search bar, you get directed to MS Word Online, a free version of MS Word.
For all the other programs, and browsers as well, hit "print" and select "print to PDF".
> Which one, the Edge browser
Yes. I hate Edge and have disabled it, but I have to give it to them that their PDF reader is much better than the one built into other operating systems. It's optimised for simplicity and common PDF interactions (highlighting, filling out forms, etc.). Plus, unlike all the other PDF readers, Edge has some excellent security features that have been implemented because of its browser nature.
The way Edge has turned into a shitty shell of its former self is a true software tragedy. It was well on the way to become the best browser available until Microsoft decided to Microsoft all over it. Still, works fine for opening PDF files.
You can save anything you can print as a PDF since what, Windows 7? And the OS comes with a PDF reader since what, Windows 8?