If you often enter purchase orders that you might work on for a period of time and you don’t want it to be processed, then you can use the purchase order type as Journal. This essentially make a draft purchase order and it won’t be able to be processed until it’s changed to a order type. This might be useful for a simple review process if you don’t want to go to something more sophisticated like workflow.
Here is a quick overview.
AX2012 R3 CU9