For those that are new to couponing it would be best to read up on the stores coupon policies which can be found HERE
As for stacking(ie: 1 Manufacture Coupon + 1 printable/zone/other coupon) is not accepted at any Walmart's across Canada(maybe few exceptions?) and is only accepted in the US. If it happened to you, then it may have been a fluke, or mistake on the cashiers part.

