[Mauzen]

Both are "rivals", so theres no simple method to do that. Moneybookers ToS (probably paypal too, but didnt check) even forbid such an exchange, your account can get locked and you lose all your money. Other risk is that people just scam you, take your paypal money and dont send anything back. So just dont do it.
Withdraw the paypal money to some bank account and use it to get Moneybookers money, thats the only legal and safe way.