You can get it straight from here. Note when you click the link it will auto download via a zip file. The demo allows you to play 10 minute matches with Manchester United, AC Milan, FC Porto, S.S.C Napoli, Santos FC, and C.A. Panaro.
Konami has also announced that “due to unforeseen issues,” the Xbox 360 version of the demo has been delayed into September, according to CVG. We’ll update you when we have more on that.
PES 2012 launches on October 14 for PS3, 360 and PC, with PS2 and PSP versions launching on October 28.