If you use a print PDF to produce a physical book, the page numbers may be important to you and your readers. Thus, you may desire that an electronic PDF have faithful page numbers. You may have noticed from the discussion about page numbers in cross-references that because the default behavior puts page numbers in the print PDF, and not in the electronic PDF, content will not always appear on the same page for the two conversions. The solution is simple—use latex.pageref to have the two conversions behave identically in this regard.