To everyone wondering if it was leaked on purpose or whatever, it clearly says right at the top: Originally uploaded to http://cdn.flamehaus.com/Valve_Handbook

To everyone wondering if it was leaked on purpose or whatever, it clearly says right at the top: Originally uploaded to http://cdn.flamehaus.com/Valve_Handbook_LowRes.pdf http://cdn.flamehaus.com/Valve_Handbook_LowRes.pdf Handbook courtesy of Valve So, they shared it on purpose and are not trying to disguise it as a "leak".