Oder received but no payment

[2cv]

Hi,

It already happens several time, the customers choose paypal payment method, but on the last step of the order (when they are redirect to paypal) they forgot to make the payment...

Is there any way to make the order valid only after making the payment ?
and/or
Can I give them a link so that they can make that last step of the order (paypal payment) ?

Many thanks!