I, "Outbox" right click the stack you want to setup printing from and choose "Stack options".
Mark "Print freight letters on transmit".
Mark "Print all freight letters on" - And choose a global A4 printer. Use this method if all freightletters must be printed from the same printer or if you have setup scheduled transmit of EDI data.
Or mark "Display the print dialog" - Choose this if you want to print freightletters from various A4 printers and use manual transmit of EDI data.