To hide or unhide a page that is hidden click on the title of the page in the Navigation Editor, then click on the switch next to Hidden so it changes to green. telling you it is now hidden. To unhide a page, click on the Hidden selection so it grays out followed by Update. After hiding/unhiding pages remember to click on the green Save in the upper right-hand corner.
Please note that you will need to take additional steps if the page that you are hiding is also in the drop-down navigation of your site too.