The MS instructions I found for exporting an entire notebook to a PDF don't seem to apply on the Mac OSX version. Is there a way to do this on Mac OSX?
At the moment, no! It is not possible. OneNote "is" / could be a fantastic program, but it does have a lot of critical limitations. A solution to your problem, which I also encountered, is to make an account for the office pack. You can do that through OneNote. Afterward, you will be able to share an online version of our entire notebook or open it at another PC or Mac.
Short answer - not on your Mac.
The easiest way to export an entire notebook as a PDF is to sync the notebook to a Microsoft account (if you're not already doing so). Then, find a Windows computer (libraries often have Windows computers with Microsoft products installed).
On a Windows computer, you'll be able to sync the notebook, and export it as a PDF. Make sure you're using the desktop version of OneNote and not the "tablet" version that you install from the windows application store.
It's ridiculous - but that's the easiest way to do it.
It is currently possible to shift-select all the pages you would like to export, Copy them, then Paste them into a Word document or something similar from which you can export to PDF or whatever format you prefer.
This is the only way I have found to export a hard-copy of multiple pages with OneNote Notebooks.