On the CIC website I read:

"Eligibility to apply from inside Canada

You can only apply for a work permit from inside Canada if:
you are in Canada because you have already applied for permanent residence from inside Canada. You will have to pass certain stages in the main application process before you can be eligible for a work permit."

Anybody knows what these stages are?
I've recently applied for PR (Federal Skilled Workers) but my work permit is going to expire in 10 weeks. Please direct me to the right source thank you!

This refers to "approval-in-principle" of an inland spousal or common-lay family class sponsorship.

So it does not regard the Federal Skilled Workers Program. Thank you David.