What is the different between preference shares and paid-up shares?

Preference shares have a dual nature. They receive a fixed interest payment for a pre determined time period (say 10 years) or for a specific stock price of the underlying company (say $40). When the criteria has been met the preference share can be converted into "common" stock or sold back to the issuer depending on the terms.

When a company needs money, it sells stock which reperesents an ownership in the company. So if a company issued shares for $10 par value but at the time of selling the stock was $50 it has a "paid up" of $40. Par value almost always means nothing. So the company wouldve sold a portion of its business for $50 a piece.