I regularly need to create PDFs with fillable form fields that can then be filled using Adobe Reader. However after a lot of research, it seems that the only tools capable of actually adding fillable form fields to PDFs are GUI tools like Acrobat and Foxit, which are also often proprietary. Note that I'm not asking for tools that programmatically fill out those form fields, of which it seems there are many - I'm asking for the inverse.
How can I add fillable form fields to my PDF files programmatically, either via the command line or some other method, such that I can more easily automate the process?
$doc->fillFormFields($name => $value, ...)