How make Pentaho Report Designer duplicate the layout for multi select input?

Question

I have a use case where the user will enter multiple billing numbers and expect a PDF that contains corresponding billing document for each of those numbers.

The current version I have built only accepts a single billing number and returns a single billing document.

How do I make it work for multiple billing numbers? I want Pentaho to generate a PDF with all the billing documents that are given as input using the single template that I have built.

Appreciate your help very much!