@Gareth I have tried using a workflow to print a version of the Sales Order that I've reformatted to look like a packing slip, but it's not ideal. Also if you are trying to do an automated on premise print to your local printers then that would not be possible without some sort of application.
We use SummitIT for this. It has been one of the best modules we've purchased for NetSuite. They can print almost anything, to anywhere in your warehouse, from any trigger in NetSuite.
https://www.summitit.com/