Update
The new version Adobe Reader XI allows to save the filled-out version of any form - special treatment with the commercial Adobe Acrobat thus isn't necessary any more.

The original answer
You can create fillable forms with hyperref
which can be filled out in the free Adobe Reader and send back to you by e-mail. A minimal example would be (replace forms@stackexchange.invalid
by your own e-mail address):
\documentclass{article}
\usepackage{hyperref}
\begin{document}
\begin{Form}[action=mailto:forms@stackexchange.invalid?subject={The submitted form},method=post]
\noindent\TextField[name=name]{Name:}\\[1mm]
\ChoiceMenu[radio,name=gender]{Gender:}{male=male,female=fem}\\[1mm]
\TextField[name=email,width=5cm]{E-mail:}\\[5mm]
\Reset{Reset} \quad \Submit{Submit} \quad \Acrobatmenu{Print}{Print}
\end{Form}
\end{document}

Your customers can fill the form, and by pressing the Submit button, an e-mail will be sent to you with an attachment called <filename>.fdf
which contains all the provided data.
You can examine this file using e.g. the free PDF-XChange Viewer: Open the PDF file containing the form, select File->Form Data->Import Data to Form...
and open the e-mail attachment you received. Now all the form fields will be filled with the results. (Update: You can even use Adobe Reader X itself: Just open the PDF file containing the form and double-click on the .fdf
file afterwards. You may have to accept to trust the document with the yellow notification bar on top, then the form fields will display the results.)
The advantage of this solution is that it doesn't require your customers to install an additional program: They can use the Adobe Reader which is installed on many systems by default. You can even create forms that sends the results directly to a script running on your server to store it e.g. in a database - see the hyperref manual for more details.
PDFCreator
only. I have used it in this exact instance before where referees for a journal article have to submit a report (with check boxes for selection and text boxes for comments). The suggestion to "Print to PDF" the actual fillable form (also a PDF created in LaTeX usinghyperref
) works like a charm, looks clean and can be easily transmitted via email.