There is no way to 'delete' a page to ensure we don't lose any data.
Instead you can unclick the 'published' checkbox in the backend. This means no one will be able to see the page and is essentially archiving the page so that we never lose the history of the site.
If you would like, you can then change the name/URL/content of the page and re-publish with new content instead of creating a new page when you next need one.