Thanks, David, for showing me how.
NOTE: This guide was apparently created by using an existing HOWTO on another subject as a template; the original text was deleted and replaced by completely new text. Unfortunately the author had change recording enabled at the time so the "deleted" text remains on show, greatly complicating the editing task. Many pages of irrelevant text had to be scrolled through to find the paragraphs that actually belonged to the new guide.
May I suggest that in future, authors who want to create a document by this method do not enable change recording while clearing the old text from the file?