Each Space has a specific defined set of people with access.

However there are times when certain information needs to be Restricted to a subset of users.
This can be done using the Restrictions facility at the bottom when you create the page, or later using Tools>Restrictions.

The list of Restrictions is the people who are allowed access to that page and any of its Child Pages (i.e. Restrictions are inherited from the Parent page)

NOTE: It is always wise to make sure you first include yourself as having both View and Edit Restrictions set before you add others.

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