I happened to witness it much as I wanted to watch it through online streaming, I watched a couple of it live until round 6, but then had problems with my internet connection so I had to see the news from my friends on plurk (lolz)
Pacman knocked Cotto twice (round 3 and round 4) and manages to give strong punches. Pretty good game to watch because Cotto also thrown some good punches but then our hero had a lot of power over the fight.
The fight ended on round 12 when the referee stopped the fight. Thus another victory for "Pacman" which got him 7 different titles for boxing.
Here's some highlights of the fight:
Sources: http://pacquiao-vs-cotto.blogspot.com/
http://sports.yahoo.com/box/news?slug=ki-pacmanwins111409&prov=yhoo&type=lgns
