FDF-files not opening properly

We have created a servlet that provides a FDF file for our clients. The FDF file is created by iText and the output looks fine. Whenever we open the FDF either from the Servlet, or from a local file, AcrobatReader starts, asks if the PDF should be downloaded, we allow that and then we see the PDF - without the values we filled in the form.

One thing that seems strange is, that regardless of the Browser, we g开发者_JAVA技巧et prompted about what to do with the PDF file that Adobe has tried to load. Anything else that clicking "open" will result in a empty Acrobat viewer window. I suspect that Acrobat forgets what to do with the PDF - but I have run out of ideas. Anyone got an idea where to look further?

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I have now solved the problem:

If you have any FDF/XFDF file, the PDF it references has to come from the same server. If it doesn't - it won't work and just show the PDF as if it was opened standalone.