A shipping order was a business document related to the transportation of goods.
In 2375, Nog asked Chief Miles O'Brien for his authorization code for some shipping orders. (DS9: "Treachery, Faith and the Great River")
Also that year, Ezri Dax cited the multitude of contracts, invoices, balance sheets and shipping orders as the reasons why she never went into her family's business. (DS9: "Prodigal Daughter")