I am sure that someone has this answer!

I am using Adobe Acrobat X to create forms. I do not have a password protections added to my forms, but I would like for the person using the form, to be able to type information into the form and save it. When we open the document, and try to save what we entered into the log, it says that we can only save a blank copy. Is this something simple that I can fix to allow the form to be typed into, and let them save it when they are finished?
 
Thanks