With Adobe LiveCycle Reader Extensions you can enable various features in PDF documents, that are available only in Adobe Acrobat Professional or Standard. This includes the ability to save PDF forms with the data users have filled in it. Reader Extensions has a simple UI, using which you can apply various usage rights to a PDF form. Apply Basic Form Fill-In usage right. Users will have to use Adobe Reader 7.0 or later.
Another way to do so is extending PDF forms using Acrobat Professional. However, the form designer can collect only up to 500 responses from such a PDF form.
See this article, for the various usage rights that can be applied using Reader Extensions.
See this article, to know how to extend PDF forms using Acrobat Professional.