If you want to add some extra specific data against a product in a printing template you can do it by adding product properties to the template.
You can find how to add new product product properties here.
When you have added the properties that you need to the product go to:
Settings - Printing Templates and click Edit on a template you want to change.
Add a new text field, type in the name of the property as you want it to be shown on the document and locate it where appropriate.
Add another text field and type in product property as it is saved in the product details in the following format:
Please note: Avoid using brackets in product property names as this may cause issues.
Resize the text field and locate it in the line with other product details.
Click SAVE and you are ready to print your documents with new product details on them.