In order to save information in the form, you need to first download the document locally or to a network drive. If you edit the information in the browser window in which it appears, your changes will not be saved.
Click the name of the document you wish to download. The form will show as a downloaded file just over the task bar on the bottom of your screen. When it does this, click the file name. It will open in another browser window. From here, click the download button in the upper, right-hand corner of the screen (a down arrow). This will bring up the standard dialog box with your local and network save options. Save the PDF in this location.
Once saved, exit out of the browser window and open the PDF on your machine. From this point on, you should be able to edit and save the file as needed without worrying about losing your changes.