Hiding a page
While in the editing mode for a page, click on the Settings tab at the top right.
Hiding Pages from Menus
Next to Visibility, untick the Show in menus? checkbox then click Save & Publish, this will stop the page appearing in your website navigation menus.
Hiding Pages from Search Engines
Click in the Page Priority options, select Not Indexed then click Save & Publish. This will tell search engines that this page should not be listed, however if the page is already listed or has links from elsewhere, search engines may still show it.