To avoid editing errors on page spreads, only one unassigned editor can edit a page at a time. The page spread will lock when an editor is working on a single page of the spread. Any other editors selecting a page on the page spread will be locked out and see the message below. Once the editor has exited the page, the page spread will be unlocked for editing by another editor.
You can assign single pages to editors. This way two editors can work on the same page spread at the same time.
They will see this message when they go to the page spread to edit their assigned page.