On Fri, Jun 7, 2019 at 12:24 AM Tim via users <users@lists.fedoraproject.org> wrote:
 
What I don't know about PDF forms is:  Are they just intended to print
out a page like you've filled it in, or are they supposed to be machine
processable to extract your typed-in data?  (Which seems a very dumb
requirement in this modern online world, with a couple of decades of
HTML forms already fulfilling that purpose.)

Yes, both, and more. 

PDF has many different versions and options and at least two different systems for defining forms and the data to fill them. I have a commercial application that uses one of the older formats, but generates tens of thousands of "official" documents with data filled in from a database and an official ink signature (as a graphic) which recipients can use as evidence to perform their businesses.

With the proper libraries, these documents can be queried and what the form-filler placed in the named data entry fields (text, number, checkboxes, etc.) can be read by machine. So, the PDFs can be computer- or user-generated and could be computer- and user-readable.

There are also complex forms (like tax documents) which can be filled out with a viewer or some browsers and submitted, either as a document, or by using embedded script, submitted over the internet. There are some benefits over HTML forms in being able to print pixel-perfect forms or save PDFs for those who need to archive their documentation. HTML printing on the spectrum of operating systems and variety of printers is more difficult to achieve.

There are a number of closed source, proprietary, commercial PDF libraries to accomplish all of these functions. Open source options are more limited. I've had great success with pdftk, which is available on Ubuntu but not Fedora due to iText licensing issues, iirc.

 
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Ted Roche
Ted Roche & Associates, LLC
http://www.tedroche.com