The added info you see at the top and bottom of the printed page is actually added in by your internet browser whenever you print something from the web. 

By default they will add the url of the webpage, the date and possibly other information.

Luckily it is easily removed, and Shopify have a good guide you can follow here: https://help.shopify.com/manual/apps/apps-by-shopify/order-printer/printing-order-documents#remove-the-header-and-footer-from-printed-pages

That will remove those bits of information completely.