Hi
For people who only have Reader, then can enter data into the form, they can submit it electronically (via email or http), but they can't save it locally. To enable this, you need to purchase a license for something called Reader Extensions, which is sold by Adobe on a per-form basis.
There are some other ways to do things that don't require reader extensions. For example, you can save the partially completed form on the server, rather than locally, as is done by the Adobe Form Manager product. There are some other techniques you can use, which will depend on the use-cases for the solution you are trying to build.
If you would like to explore this further, we have considerable experience with this, and would be glad to help - email info-at-avoka.com.
Regards,
Howard
http://www.avoka.com