have Acrobat 9.0, 10 yrs. Pop Up Message when Printing - "Must sign into One Note the first time before printing." What is this? Never happened until today.

As One Note is a Microsoft product, you should ask the Microsoft forum. But Luke Jennings gave you the correct indication. Change back your default printer (Windows printer settings) to what it was and it should be OK.

When you install office, Windows often configures OneNote as the default printer, there are ways to disable OneNote both temporarily and permanently.

https://smallbusiness.chron.com/disable-microsoft-onenote-44259.html