Importing data into PDF form

I would like to import data such as dates, text and numbers into existing fields in a pdf.
Please help, as I cannot find any solution despite multiple web searches.

It’s quite easy to extract the text content (including numbers) from a PDF.
Maybe doing that would be a good starting point.

Yvan KOENIG running El Capitan 10.11.5 in French (VALLAURIS, France) vendredi 1 juillet 2016 11:40:51

Extracting data does not provide the details that are required to import data into a PDF to populate its fields.

We aren˜t sooth sayers so it would be useful to give a link to such a PDF.

Yvan KOENIG running El Capitan 10.11.5 in French (VALLAURIS, France) vendredi 1 juillet 2016 23:45:13

I wish I could provide a sample AppleScript but I cannot find a method or a script to write an Applescript that might run or call a pdf Application. The closest I come to that is employing an Automator script to manipulate a pdf. None of the Automator workflows however contain a method to import data into a PDF, so as to populate targeted PDF fields, although exporting general metadata from a PDF is allowed.
For example, PDF Pen allows exporting data but does not allow importing data into defined fields in a PDF.

In summary, I am unable to come up with even a failed AppleScript attempt at populating fields, as I can’t find any application on OS X that performs this PDF function. I was hoping that an AppleScript function might exist outside of an application to perform this function.