I've done SJU many times. You will clear immigration in SJU, claim your bags, then go through Customs, then pass your checked bags back to continue to YYZ, then you'll exit on the way out in to the land side of the terminal. Right before you get to TSA, you see a USDA scanner and you'll have to pass your carry on bags through that, then head to TSA to get screen for entry to the air side of the terminal and complete your flight to YYZ.

Last edited by wilsonck; 10/12/2016 11:23 AM.