Since some themes and plugins already include a print stylesheet or allow you to build your own, Jetpack doesn't change anything in the print output.
If you want to customize the print output on your site, you can add specific rules to your theme stylesheet or to your custom CSS editor under Appearance > Edit CSS in your dashboard.
You can use CSS media queries to create specific rules that will only be applied to the print output. You could hide the header, the sidebar, and the footer for example.
You can read more about it here:
http://www.joshuawinn.com/css-print-media-query/