If you are a Canadian citizen within the first year of your citizenship over the age of 18 and you've lost your citizenship certificate, you must contact Immigration, Refugees and Citizenship Canada:
I’ve lost my citizenship card/certificate. How do I replace it? https://ircc.canada.ca/english/helpcentre/answer.asp?qnum=048
If you have lost your PR card, please see the instructions here:
Apply for, renew or replace a PR card: About the process
https://www.canada.ca/en/immigration-refugees-citizenship/services/new-immigrants/pr-card/apply-renew-replace.html