QUESTION: What is FDF?
stands for "Forms Data Format." FDF is a
file format for representing form data and annotations
that are contained in a PDF form.
The FDF format was invented by Adobe Systems Incorporated, and it is
based on the PDF format. You can find a detailed specification for the FDF
format in Adobe's PDF Reference.
The FDF format can be used in a variety of workflows. Here are a couple of examples:
Sending form data to a server and receiving modified form data back from the server. This workflow
would look something like this:
Archiving form data. This workflow would look something
- Form data is submitted to the server in FDF format. (Typically, this would happen when
a human user at a client machine clicks a "Submit" button on the form.)
- On the server, the FDF data is modified.
- The server sends the modified FDF data back to the client.
- At the client machine, the fields in the form are populated with the modified data.
You might be wondering why you'd want to archive an FDF file containing the data
for a PDF form instead of simply archiving a uniquely named version of the entire PDF form with the data
included in it. There are two reasons:
- A human user uses Adobe Acrobat or another PDF-editing/viewing application
to export the form data in FDF format. (To do this
in Adobe Acrobat 6.x for Windows, click Advanced > Forms > Export Forms Data and
choose Acrobat FDF Files (*.fdf) for "Save as type." The procedure
might be different if you're using another version of Adobe Acrobat.)
- The FDF file is saved in the company's archives.
- To look at the form data, a human user would use Adobe Acrobat or some other
PDF-viewing/editing application* to open the FDF file;
this would cause the PDF-viewing/editing application to 1) find the PDF form from which the form data was
exported, 2) load the form data into the form, 3) display the form with the loaded
data on the screen.
IMPORTANT NOTE TO DEVELOPERS: An FDF file contains the filename and location of the PDF form
from which the form data in that particular FDF file was exported. Adobe Acrobat (and any
PDF-viewing/editing application that supports PDF forms) relies
on that filename and location in order to retrieve and open the
appropriate PDF form when opening an FDF file.
In other words: when opening an FDF file, a PDF viewing/editing application
the PDF form from which the form data was exported is available at the
- An FDF file containing form data for a PDF form is much smaller than the
file containing the PDF form itself, so archiving FDF files requires less
storage space than archiving PDF forms.
- Some software that people use to view and interact with PDF forms does not allow
the user to save a filled-in PDF form. For example, the free "Adobe Reader"
software does not allow this.
Therefore, if you are a developer that is considering
implementation of a system that archives FDF data, you'll want to
make sure that your system has a reliable method of storing the
required PDF forms in known locations. Otherwise, it will not
always be possible for PDF-viewing/editing applications to retrieve and open
the PDF Forms when they are needed.
Creating your own FDF files
As mentioned, the two workflows described above are just
examples of how you can utilize FDF data. Both of those workflows
rely on a PDF-viewing/editing application such as
Adobe Acrobat for creation of the FDF data.
However, you don't have to rely on a PDF-viewing/editing application to
generate FDF data — it is possible to generate FDF data yourself, and
depending upon what you need to accomplish, it might make sense to do just that.
For example, if you have data stored in a database,
it would be possible (if you are a programmer or if you have access to
someone with programming skills) to extract data from your database
and put it in FDF format. Or, if you have a Web site where site visitors enter
data into an HTML form, you or your programmer could write a script to
convert the data entered by users to FDF format. As stated below,
the FDF format is
described in detail in the Adobe PDF Reference, so you'd
need to read the relevant sections of that document to gain an
understanding of the FDF format before you'd be able to generate your
own FDF data.
Populating PDF forms with FDF data dynamically
You don't have to rely on a PDF-viewing/editing application to load
FDF data into PDF forms. Instead, you (or your programmer)
can use a programmer's toolkit
to put FDF data into your PDF forms automatically.
Citation Software sells two programmer's toolkits that make it easy to
populate PDF forms with FDF data automatically:
Depending on which of these programmer's toolkits you're using, you
might even be able to put graphics as well as text into your PDF forms.
How to get more information about the FDF format
The FDF specification is part of Adobe's PDF specification, so
you'll find the FDF specification in
Adobe's PDF Reference.
See also What is XFDF?
See also What's the difference between FDF and XFDF?
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