I have been searching a way to print my Canada Post shipping labels automatically on my Shopify account but I couldn't find any way to do it so.
I have currently up to 47% off on Canada Post which is greater than what Shopify Shipping with Canada Post offers me and to be honest I do not want to waste my money on Shopify shipping.
It mustn't be hard for Shopify to allow print shipping labels on our admin panel while on the other side they allow my customers to see my actual Canada Post rate at the checkout because it is connected via API from Canada Post Developer center.
If you've negotiated discounted shipping rates with Canada Post, then you can display your negotiated rates at checkout by connecting your Canada Post account with your Shopify store. But, I don't think printing the Canada Post shipping label with the same rates is possible directly from Shopify with your own Canada Post account. Do check out this guide on the same: https://help.shopify.com/en/manual/shipping/setting-up-and-managing-your-shipping/enabling-shipping-...
However, if you are open to using an app to handle this, you could try our Multi Carrier Shipping Label app that would do the job for you. You can connect your own Canada Post account and display negotiated rates at checkout as well as print Canada Post shipping labels with ease. You could also check out this video on how the app helps you with the same: https://www.youtube.com/watch?v=K1HwHBvxOO8&t=55s
Hope this helps you!