Magento 2 Order Approval Rules enables admin to place some principles for clients to place an order and ship it to get admin approval prior to making a payment.

Key Features:

1. Admin is permitted to produce rules or set terms of order purchase by clients.

2. Enable or disable the module in the rear end admin panel.

3. Approve the orders from bulk by rear end admin panel

4. An automated message or email will be obtained by the client on order rejection or       approval by admin.

View Frontend Demo

For more information visit here Magento 2 Order Approval Rules