If you're non-resident in Canada, you only have to pay tax in Canada on Canadian-source income. Unfortunately, yes that includes a pension.

To be non-resident you have to spend at least half the year outside the country and have no residential ties to Canada like property, dependents, bank accounts, health insurance, etc.

See: http://www.cra-arc.gc.ca/tx/nnrsdnts/ndvdls/nnrs-eng.html

Do you have to pay tax on your German earnings (earned in Germany, which you already pay tax to the German authorities on)? Almost all countries only tax you on the money earned (approximately) within their borders. So for most 'expats' it amounts to taxing interest and dividends, and maybe rental income on your old house.

Not so the USA, which has a claim on all money earned by Americans world-wide. There's a ~U$100k earnings exemption (so many people aren't paying much tax back to the USA), but high-earning USA expats are in a different tax-world from their overseas colleagues.