how does the CIC figure that out and what could be the consequences- any idea?
CIC might check up on the persons credentials by contacting their past employers or universities. It is also possible that somebody who knows that you forged your documents has an argument with you and decides to rat you out.
If you are found to have forged documents to get your PR, if you don't have your PR yet, obviously they will throw your application out. If you already have your PR, they can revoke it and even if you have already gotten your PR and after that citizenship, they can revoke your citizenship as it was based on the PR you gained by misrepresentation.