Expiration date

Hi all…
I may be totally stupid but i cant figure out how to give a validity/expiration date to a download package?
The fact is:
The pdf documents i offer to be downloaded contains travel offers and of course the price are only valid for a period.
How could i define when the time is up the offer cant be downloaded anymore?

Thanks for help

thanks!!!

Thanks i’ve bought a pro licence, but i can’t find where is the licence number to fill the plugin info in my wordpress? Thanks for help