Question

If I wanted to add new functionality to an existing InDesign feature (say, pdf export), can I do that with a custom plugin, or would I have to make a completely new pdf export plugin altogether, first duplicating all the functionality of the existing pdf export feature, and only then adding my new functionality to that?

Answer 1

If it was something simple, you could have an event listener that would listen for a beforeExport event with InDesign’s javascript. And, within the handler, you could run a script before exporting to pdf.

var doc = app.activeDocument;

doc.addEventListener('beforeExport', beforeExport, false);

function beforeExport(e) {
   alert('hey');
   // Do stuff ...
}

Otherwise you would probably need to go the plugin route. You can check the InDesign SDK to see if there is an API for pdf export.