A text file of a few pages and several paragraphs was read into LibreOffice Writer and needs to be double spaced throughout the document. The sequence:
Format -> paragraph -> Indents & Spacing -> Line spacing -> Double
affects only the paragraph where the cursor is positioned. Searching the web and help has not turned up a way to double space the document. (Although I'm certain I've done it before. Alas, I've got CRS (Can't Remember Stuff) syndrome.)