When a PDF export is generated different footers are defined in CSS for various parts of the document, i.e. the title page, front matter, the TOC, Section 0 and the remainder of the document. The title page numbers are not displayed, the front matter, TOC, and the first chapter (Section 0) have lower case roman numerals as page numbers, and the remainder of the document, starting at Chapter 1, have decimal numbering starting at page 1. So essentially, the first half of the document has roman numeral page numbers in the footer and the the second half has decimal numbers.
Although at first it looked like it as going to be straight-forward, so far we have not been able to find a way to do this.
We can not modify the html for sections headers in VE. If we could this may help.