What is required
All international postdoctoral fellows are required to have a valid Immigration, Refugees & Citizenship Canada (IRCC) work permit prior to assuming a postdoctoral fellowship. Additional information regarding postdoctoral fellowship procedures can be found here.
If you are looking to gain work experience and are not doing research furthering your PhD, please see Waterloo International's Researchers page.
Becoming a postdoc
More information regarding postdoctoral fellowships is provided by University of Waterloo's Graduate Studies and Postdoctoral Affairs website.