If you do not want to invite users to your page manually you can use an implicit mechanism by inheriting all admins, co-admins and members from the parent page.
When this option is enabled for a page, the admins, co-admins and members from the parent page are automatically becoming the same member role and the same permissions in the current page without explicitely inviting them. In addition, as soon as the members of the parent page are modified these updates are automatically propagated to your page - without any interaction.
You can enable this option on the page settings (section "Do you want to inherit users?").