In most cases, the page (saved or printed) is "as is."

With the web page on the browser, you can use the zoom controls.

For printouts, use the Preview option to check it before printing.

Thanks for weighing in, but your answer didn't address my problem. I'm not talking about the size of the web page. I'm talking about the size of the Explorer window where I save the web page to my hard drive. THAT window is now full screen, and I can't minimize it. It's annoying!

Ahh, Sorry. I misunderstood what you wanted.  :-(

Are you talking about not being able to go from full screen to the partial window, or you can't change the frame of the partial?

You may have a corrupt xulstore.json file. https://support.mozilla.org/en-US/kb/changes-toolbars-and-window-sizes-are-not-saved

Can you open the system menu of the file picker window via Alt+Space to check whether the window isn't maximized?

@FredMcD -- I tried that, but it didn't solve the problem either. Thank you for the idea, though!

@cor-el -- I tried Alt+Space. Maximize was disabled, and no Minimize option listed on the menu. However, I clicked on the Restore option, and the window shrunk back to normal size -- so Alt+Space+Restore works. Thank you!