On clicking on purchase order item from the list of purchase order, the user would be able to access the purchase order details module as shown in the image below. This module allows you to see the full detail of a single purchase order.

You have the option to reverse a Purchase Order by clicking the reverse button marked by the red arrow in the image below. 

image 2.0 landing screen after clicking on an individual Purchase order, reverse PO is marked with red arrow.