As many as you can afford the gas for :evil: but, guess you mean at one time behind each other. maybe someone will be able to answer your :question: . Might try goggling Canada laws on trailering.
Rules of the road are decided on a provincial level...check out... http://www.rvda.ca/ProvRVRegs.asp for details. It does not give specific rules on the number of trailers, but it does advise of maximum length of tow vehicle and trailer for each Province, as well as other regulations regarding RV's. ... Hope this helps...