You won't get PADI certification in Cuba. PADI is an American company and is prevented from doing business in Cuba by the American government. The trade embargo is still in place.
Why do you want to go to Cuba? It's cheap and it's easy for Canadians to go for a vacation but there are better places to dive in the Caribbean like Cozumel or Roatan. I spent a week in Cayo Largo and found it to be a bit disappointing by comparison. There were no problems with rental equipment but the diving just wasn't as exciting as I hoped. Not a lot of fish, so-so coral, lots of lionfish.
Cuba is a fascinating place to visit if you like to travel around independently. But if you go on a package trip to a resort in Varadero, Cayo Coco, Holguin, etc you will be spending all your time with other Canadians and being waited on by well educated Cubans who can't find work in the fields they were trained for.
If you want to focus on diving and getting more PADI certification then go to Playa Del Carmen, Cozumel or Roatan.