Yes, you can open as many as Demat account you would like with the same PAN card. There is no restriction on this.
But note: 1. Most broker charge AMC on demat account. You will have to pay this yearly fee to keep the account active. 2. You cannot apply multiple applications in an IPO as IPO application should be unique by PAN number.
Also note that you cannot open more then 1 trading account with a particular broker using same PAN number.