Yes! You can add your own message (and logo, if you choose) that will be added to each packing slip! Do this by going to Stores → Edit.
You can also include a personalized message on the packing slip when submitting an order by checking Include a personalized message on the review page. Order prices will be hidden from packing slips with a gift message for US domestic shipments and shipments within the EU from our Europe location.
Note that in response to Covid-19, we're fulfilling part of our orders in partner backup facilities. Orders routed to these facilities won't have customization options for packing slips or logo printing on the package.