A PDF document that contains interactive forms can be thought of as having a form data layer superimposed on the primitive graphics layer. While a PDF file contains both layers, a Forms Data Format (FDF) file contains only the data layer. An FDF file is smaller and simpler than a PDF file, and can be imported into a PDF file that has a form structure that corresponds to the form in the FDF file.
After a user has edited a form in a PDF file that has been created from an SPS, they can do the following:
•Submit the edited form data to a server as an FDF file, or submit the entire PDF file containing the edited form data to a server
•Extract form data from the edited PDF file to an FDF file
•Extract form data from the edited PDF file to an XML file
These actions, and also how to design fillable PDF forms so that the user can submit form data to a server, are described in the sub-sections of this section.