The drawing fitted the sheet correctly, and I had picked the right size of paper, but could not understand why it was one of four pages, the others all being blank.
I've just re-opened it though, and looked at the Page Setup / Layout tab you say.
I'd never previously used that because everything worked otherwise, but it looks as if the added pages were due to those "rows" and "columns" settings. They were both set to 2, I don't know if by default. I can only assume that's to allow spreading multiple elevations over extra printed pages so they are of legible size.
The manual I mean is that via "Help" on TC itself - and it has only 800 or so pages.
However, I had another look at it, and was surprised to find sections on printing, viewports and rendering, beyond those on architecture and woodwork. I'd not seen them previously, and think they are recent additions. That on Viewports is just their use in Paper Space for different views of the drawn object, or to make minor changes; but apparently all in 3D - so not helpful to me!
I know we're supposed to use that Viewport system but I don't know why and how, though I assume it has particular advantages over simply copying and pasting the image (adjusting its size to suit). Nor where to find it, and I have searched very carefully.