Every now and again this happens, and I end up just trashing the whole document and starting again: I hit what I think is cmd-shift-7, to take out extra spaces and email nonsense, and instead hit something close to it, and turn the whole document into a hypertext link. (This time, it’s also turned the background pink.)
What is this, is it a toggle, and how do I undo it, please?
Shift-Cmd-8, and applying a linked note to the selected text? The inspector would show you the Comments & Footnotes pane in this case, with a new note ready for entering text. Just hit Edit > Undo (Cmd-Z) to undo it and then use the correct shortcut.