What is dual citizenship?
Every country decides whom it considers to be a citizen. If more than one country recognizes you as a citizen, you have dual citizenship.
You do not apply for dual citizenship and there is no related certificate. Canadians are allowed to take foreign citizenship while keeping their Canadian citizenship.
If you are a permanent resident but not a Canadian citizen, ask the embassy of your country of citizenship about its rules before applying for Canadian citizenship.
For more information about dual citizenship and important things you need to know, see the Foreign Affairs, Trade and Development Canada brochure Dual Citizenship.