If you don’t want display the pages into Page Menus you can override the page menu templates (tree.html, dropdown.html, footer.html) checking if the pk of current page is not in unauthorized_pages template context variable.
Here’s a example of customization of original tree.html template:
# ...
{% if page.in_menu and page.pk not in unauthorized_pages %}
<li class="
{% if page.is_current %} active{% endif %}
{% if not page.is_primary and forloop.first %} first{% endif %}
{% if forloop.last %} last{% endif %}"
id="tree-menu-{{ page.html_id }}">
<a href="{{ page.get_absolute_url }}">{{ page.title }}</a>
{# wrap the next line with 'if page.is_current_or_ascendant' #}
{# to only show child pages in the menu for the current page #}
{% if page.is_current_or_ascendant %}
{% if page.has_children_in_menu %}{% page_menu page %}{% endif %}
{% endif %}
</li>
{% endif %}
# ...
The unauthorized_pages variable is inserted into template context by context processor 'mezzanine_page_auth.context_processors.page_auth' (reference Template Context Processors)