Everything I've read on here and elsewhere indicates that "whispernet" works fine in Canada. For example, see the thread here at
https://www.mobileread.com/forums/sho...d.php?t=108343 . The main problem that some might have is patchy 3G coverage in more rural areas, but if you can connect your Kindle to WiFi (either on your home network or in a library or cafe, perhaps) then you should have no problem downloading documents you've emailed to your Kindle.
Bear in mind that document delivery via 3G will be charged for, whereas delivery via WiFi is free - you can set the maximum delivery charge on the "Manage my Kindle" web page (if you set it to 0 and/or use the "@free.amazon.com" email address, Amazon won't deliver documents via 3G).