Agree with both
noscaf2014 and
trumprefugee.. if you are a citizen, go through a channeler and you would get it really quick.
But,if you are a PR or on visa, it is best to do it as soon as possible, assuming that you are confident with your score and profile getting picked up in one of the draws. I started 1 month before getting the ITA and it took me 3 months to get the PCC, so it worked out well.
Another thing, though I'm not entirely sure of it, the PCC for the current country should not be more than three months old when you send all your documents. Although I didn't face this scenario, I have read this in several places in this forum. Just thought you should know.