Selecting text across forty pages by hand is miserable, and PDF selection rarely behaves. Taking the whole text out at once is faster.
A PDF exported from a word processor or generated by a system carries the real words inside it, and they come straight out.
A PDF made by scanning or photographing paper carries a picture of the words instead. Nothing here can copy those, because as far as the file is concerned there is no text on the page, only ink.
Reading those needs text recognition, which is a different job and not built yet. If your document comes out empty, that is what it is telling you.
No. You get the words in reading order, not the columns and tables around them.
It is a scan. There is no text in it to take.
No.