Page Numbers on Presentation PDFs

When exporting a presentation to a PDF it would be helpful to have the ability to add page numbers to the bottom of the page. It can help uses follow along better if on a guided presentation (i.e. as you can see on page number...) are aid in organization of a presentation by the presenter. Ideally it would be nice to have the option to add the page number directly into the presentation itself and have the numbers automatically adjust as pages are added or removed rather than manually adding a number to the bottom of each page (this could also be used to create a TOC or reference numbers for an agenda) but if the pages numbers in the exported PDF should be the minimal goal.