We apologize for the delay, we are not sure why your message went to spam.
There is not a way to change the number of pages in a PDF, however as a work-around, you can create additional PDFs and Field Map Layouts then use conditionals and/or conditional statements to dynamically change which layout is used to produce the final PDF.
Our new plugin, E2Pdf, does allow the number of pages to change depending on the data.
Let us know if you need additional support, as we remain at your service.