You can order the paper version through your Toyota dealer or the Toyota Materials Distribution Center or your favorite discount Toyota parts source. (for cheaper, you could check eBay or in the glove box of a wrecked unit at a junk/scrapyard.)
Or, you for a small subscription fee, you can download it from Toyota:
US and maybe Canada:
http://techinfo.toyota.com/
Europe/UK and maybe Australia:
http://techdoc.toyota-europe.com/
If you just need some basic information (such as you have a rental car), you may want to read the owner-generated User Guide:
http://john1701a.com/prius/prius-userguide.htm
or the Toyota UK Prius' Brief Guide:
http://www.toyota.co.uk/bv/OwnerServ...ides/PRIUS.pdf