A user needs to search across all mailboxes ("All Users") and export those search results (e.g., for legal discovery), but they should not be given full "Administrator" privileges to the entire Archive Manager configuration.
By default, standard users can only search and export their own archived mailboxes. The ability to search the entire archive ("Search All Emails") is restricted to Administrators unless a specific Security Role is configured.
You do not need to make the user a full Administrator. You can grant specific "Security Actions" to a custom role in the Archive Manager Administration Website.