There is a free PDF viewing program that allows you fill out fillable forms and save the changes, to be edited later if need be: PDF-XChange Viewer.
After you install PDF-XChange Viewer, open your fillable PDF form (right-click and choose Open With… if PDF-XChange Viewer isn’t the default for opening PDFs).
Download the free version of PDF-XChange Viewer
Fill out the form.
Click on File > Save, or just press Ctrl+S.
Close the file. If you open it again, you will see that your changes are still intact! In fact, even if you open this file with Adobe Reader, you will find that your changes are still there.
That’s all you need to do!
PDF-XChange Viewer is a great all-purpose PDF viewer, and the ability to save filled out PDF forms makes it even better!