Out of the box when you visit a page that you cannot reach, you get this error:
"The page you were trying to reach could not be found. This could be because:
The page does not exist.
The page exists, but you do not have permission to view it."
It would be helpful to customize this message to state explicitly if a person cannot view a page due to permissions and how to request those permissions.
I just checked and the 404.vm file is still located in <confluence_install>/confluence as described in this old post from version 4.x: Customise Confluence Page Not Found page
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