WooCommerce has a standard mechanism for adding “meta” information to a product, and our built-in simple template will include this information. This is the same extra information as you see in WooCommerce’s built-in order notification emails. So, as long as whatever plugin or code it is that allows/records extra information for a product is using this mechanism, it will be included.
If your print-outs are being generated by a third-party plugin (e.g. WooCommerce PDF Packing Slips and Invoices), then you will have to refer to that plugin’s documentation to see, but generally they will also be including this information in the same way, since shop owners almost always want to see this information and hence an order summary excluding it would be of limited of use. (Of course, you can also look at the PDFs being generated by the plugin, and seeing what is in them).
For further customisations to the output, please see this FAQ.