When viewing an 'Order Edit' page, you can view the order history for that order. This option will only become available when you have made a change to an order, such as adding a product or changing the order price. At the top of the page you will see the 'Order History' button as shown below.
When you click on 'Order History' you will see the order history. Use the scroll buttons in the bottom right hand corner to view any changes and be sure to press the 'X' to close the order history. When looking at a particular version of changes, you can view when and which user made the changes as shown below.