How do I process FDF files created by the Acrobat Forms plug-in?

[ The files are uploaded with content type = application/vnd.fdf ]

To update/complete or recover data from a FDF you need adobe java classes which are JNI for Adobe DLLs.

I think it is available in Abobe's site

There are some caveats at the site. Read it first before jumping in.

And as for running it in VisualAge, you need FDFtk.jar file and the JfdfTk.DLL in the VAJ's classpath.