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Library and command line tool for generating FDFs
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PDF-FDF is a Ruby library and command line tool (pdffdf) to help generate the FDF files necessary to fill out forms present in PDFs.

It's especially useful in conjunction with the pdftk tool.

Typical Workflow

In the following examples the file input.pdf is the original PDF with form fields, output.pdf will be the generated PDF with form fields filled out.

  1. Create a YAML file that contains all the form fields:

    pdftk input.pdf dump_data_fields | pdffdf -ln > fields.yml

    This will generate a YAML file that contains all the form fields. Additionally each field will be given a unique value starting with 0 so that you can visually identify the form fields in a test PDF.

  2. Generate a test PDF so you can figure out which form fields have which names:

    pdffdf -g fields.yml > test.fdf pdftk input.pdf fill_form test.fdf output output.pdf flatten

  3. Open the test.pdf file and the fields.yml file. Using the test.pdf file as a guide give a meaningful name in the alias field for each of the form fields you care about.

  4. Remove the generated form field values:

    grep -v ' value:' fields.yml > master.yml

  5. Fill out values for the form fields. You can set the values directly in the master.yml file however I recommend that you create a new YAML file that only contains the fields you are interested in filling out. PDF-FDF can merge an unlimited number of YAML files into a single form field set. For this example we'll say that you created a new file called myfields.yml that is based on the master.yml file. Also note that in your myfields.yml file you only need to specify two keys for each form field: alias and value. The other values will be found while merging with master.yml.

  6. Create your filled out PDF:

    pdffdf -g master.yml myfields.yml > form.fdf pdftk input.pdf fill_form form.fdf output output.pdf flatten

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