To update the page restrictions on a page hover over the page restrictions column for the page you want to update.
Select the edit icon when it appears to open the edit restrictions dialog.
There are three restrictions options
Anyone can view, Anyone can edit
Anyone can view, Some can edit
Some can view, Some can edit.
Select your restriction level and select Apply.
If you choose an option that limits edit/view access you can select users and choose their specific permissions before you select Apply.
Page Restrictions vs Space Permissions
Page restrictions allow you to control who can view and edit a page. This is good for ensuring that changes can only be made by selected people, or ensuring pages aren't shared until they are ready.
Applying restrictions to a page does not prevent other users from deleting or archiving that page.
Deleting and archiving functions are controlled by space permissions. This is separate to page restrictions. Users can delete and archive pages inside Panorama based on the permissions assigned in Confluence.