You can customize the look of the print output by customizing your theme stylesheet, or adding specific rules 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/