Thanks all for the suggestions.
And thought I'd ask Adobe tech support for their suggestions too.
This is using Adobe Acrobat DC Pro
As was pointed out here, if you choose Organize, you'll get the "thumnails" which you'll have to enlarge by moving the slider found in lower right of screen. All these years of using Adobe and I avoided thumnails because they were too small
Go back to Organize if you've clicked on a thumnail and you need to close the full page view. (i kept trying view for that)
Despite what online documentation implies, the only way to use drag/drop to append pages to other pdfs is to have the other pdf(s) open in other Adobe windows. (drag an Adobe window off to the side) You can't drag and drop pages to existing pdfs that are say just sitting closed on your desktop or in a folder.
And the weaknesss in the drag/drop pages to other open pdfs is that you can only copy not move. so you have to manually delete each page or selection after copying.
Still, I'll try that method for a while to see how confusing it is on big file to be broken into many.
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The problem with the Extract, unless I'm reading the documentation wrong, is that you can only extract to one file per Extraction. So I'd have to go thru the entire document, either select or note the page numbers, then Extract w deletion. Then repeat the process for each additional new pdf because the page numbers will change each time I do an Extract. That's a waste of time. I think Capt C's method is similar but doesn't require writing down page numbers.
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Never realized it, but a 3rd party app I have, EverMap' PageSplit apparently will allow me to Extract different pages to different new pdfs all at once. So I'd only have to go thru the big pdf one time and note down the pages to extract to which new pdfs.
Len