Unless some other smart person on the forum has come up with away I don't believe there is a way to do if the sales order has been previously completed.

If that sales order is not completed,  I would assume you could do a negative invoice.   (Note I can't say I have tried this but it should work).

Other than that, if the order is completed, I think you get to re-enter the sales order.

If you are retaining Sales Orders/Quote History, you could create a new order and than use the Copy From feature in Sales Order Entry to copy from the original sales order.  This would effectively restore the sales order just as a different order number.  Launch Sales Order Entry, click the # button, click the Copy From button.  Change the Copy From drop box to 'Sales Order/Quote History', enter the original sales order number as the Copy From Number and click OK.