This will do:
select p.PermissionID, p.PermissionDescription, a.PageActive, a.UserID
FROM permissionTbl p INNER JOIN activePermissionTbl a ON a.PermissionID = p.PermissionID
UNION ALL
(select b.PermissionID, b.PermissionDescription, b.PageActive, b.UserID
FROM
(select p.PermissionID, p.PermissionDescription, '' AS PageActive, a.UserID
FROM permissionTbl p INNER JOIN (SELECT DISTINCT UserID FROM activePermissionTbl) AS a ON 1 = 1) b
LEFT JOIN activePermissionTbl a ON b.PermissionID = a.PermissionID and b.UserID = a.UserID
WHERE a.UserID IS NULL)
ORDER BY 4, 1
SQL Fiddle[
^]