Don't have any experience with either peach puree or pectic enzyme, but from what I've read all you're trying to do it dissolve some of the pectins floating around in the beer given off by the peaches to clear it up. Therefore, I'm not sure why you'd add it before fermentation when there isn't any pectin yet.
I think you're probably fine right now to add it in secondary. If you are kegging this batch, I could also see adding it directly to the keg, but then you'd probably have to keep the keg a little warmer for a few days for the enzyme to act. I guess the other thing to do is to take a look at your beer. Is it really cloudy from the pectin? If its not, you might be able to get by without it. But that's just me guessing