Freely Available PDF Form Viewers and Savers
From Scribus Documentation Project
The best viewer for PDF forms is Adobe Reader, as it fully supports the whole PDF forms feature set. Moreover, Firefox can display forms with the Reader's "nppdf" plugin. Okular in KDE 4 will support PDF forms as well, but it remains to be seen how complete the support will be.
CABAReT Stage is proprietary though freely available for personal use, and has both Windows and Linux versions. It can have some problems (at least in Linux) with fonts, and perhaps some other factors for proper filling out of forms. The free versions have abilities for editing PDF forms, but will introduce a rather ugly "watermark" in the background while doing so – one must purchase a version to prevent this. However, the most important feature of the gratis version of CABAReT Stage is its ability to save the content inserted into PDF forms.
Linux users should be aware of the fact that CABAReT Stage may not work at all or even freeze your desktop (as experienced on OpenSUSE 10.3). As a workaround, you can open a PDF form in Adobe Reader, fill it out and print to a PostScript file. Then open the PS file in GSview and convert it to PDF.