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Setting your default print settings to “duplex” (meaning that both sides of the page are used) can significantly reduce paper usage and, with lengthier documents, makes a sheaf only half as thick – more portable, lighter, easier to staple, etc!
This PDF summarises how to achieve this using Windows 7:
http://www.kent.ac.uk/smsas/greenimpact/resources/Duplex_Printing.pdf