How can I get the thing at the bottom of the screen back?

I won't try to guess what 'the thing at the bottom of the screen' means.

Press F11 - does that help?

If not: In general, if there are edges of a window that you cannot see because they extend beyond your monitor, there are several ways to get those edges back onto your monitor. Here's one way: Click on the title bar at the top of every window and hold down the mouse button. Now drag the title bar bar until the missing edge reappears on the screen.

If that doesn't help, it's possible that you have put yourself in kiosk mode. To get out of kiosk mode, see the instructions in How to set up kiosk mode on Windows 10 October 2018 Update.

"so that when I am working on a document,"

Hello,

The question is still not clear. Can you tell us which screen or program you're talking about, we can help. It would be great if you can share a screenshot for this issue.

Regards.

No, F11 did not do anything.  Yes, I know how to drag the edges around. It doesn't do anything,.    I am not going to read an article on how to set up Kiosk mode when what I want is to get out of it. Either one or the other must surely be able to be fixed by a click of the button - either setting it up or closing it.

You know, I cannot predict what problems I am going to have next until they happen, and they happen when I am very busy trying to create a document. 

I already have a screen that wanders - goes off to another screen and so I end up typing blind, unitl it comes back. I already have to sign in 2 x before I can access anything when I turn on this computer. When is Microsoft going to admit it screwed up?  I don't have time to fix all these nuisance things. I am just asking that I be able to see the page I am on, and the total number of pages, which should appear at the bottom of the WORD docx. And to be able to scroll down.  I never had these kinds of problems before, not ever, not in 1991 or never, until I got Windows 10.