An integral part of the EU General Data Protection Regulation (GDPR) compliance is producing appropriate documentation, which includes a privacy notice / privacy statement. 

This privacy notice has to be easy accessible for any user.  The preferred way to display this notice is to have a permanent menu item, normally in the footer of the page. After clicking the user is shown a page with the privacy notice.

At the moment Atlassian Confluence does not provide such a mechanism out of the box.

You can add a custom html for your footer, but that kinds of breaks the design of the standard footer. Furthermore, if your wiki does not allow anonymous usage, you have to host that privacy statement on an external website outside the wiki, as users who just visit the login page are not able to see privacy statement on the wiki page.

To make life easy, 

• Add a Menu item "Privacy notice" in the the Administrator menu
• There you can add the text for your privacy notice
• When activated the a privacy notice menu item is shown in the standard footer of the wiki where it says "Powered by Atlassian Confluence 6.10.0 ..."
• After clicking the item It will show a page with the text of the privacy notice to any user, regardless if logged in or not.
• Optional (but highly recommended): The privacy notice is shown to new users at the first login and the users have to accept it, before they can start using the wiki.