I'll add on to Paul's reply.
You have three choices:
1) Look to purchase the software, as Paul suggests
2) Use the Reader Extensions functionality that exists within Acrobat X (or earlier) Pro. This allows the basic form fillin/save functionality, but is subject to license limitations for the number of users.
3) Load a new Reader Extensions trial credential from the trial page http://www.adobe.com/devnet/livecycle/trial.html and add that updated credential to your server. That will enable the functionality for a few more months.