We rarely think about it now: they are always there. Books have page numbers. If they didn’t we’d have difficulty navigating around in them. Obviously an index without page numbers would at best be a minor help (“just after the middle” isn’t a wildly helpful locator). The convention that odd numbers fall on rectos and even ones on versos is almost universally followed. Starting at page 1 and numbering onward is common, but the more academic a book becomes the more likely it is to acquire two sequences of page numbers: lower case Roman numbers for the front matter, and Arabic numerals for the rest of the book. Nowadays we often find books with more number sequences: the index, the bibliography, notes, appendixes and other back matter elements are sometimes given their own pagination sequences. This is often the case in textbooks, and enables extra, late arriving material to be inserted into the book before the back matter without the delay and cost of repaginating the remainder of the book.
Naomi S. Baron’s piece in Slate’s Lexicon Valley tells us about the origin of page numbers. It is an adaptation from her Oxford University Press book Words Onscreen: The Fate of Reading in a Digital World. (Linked via The Digital Reader)
Apparently only about 10% of manuscript books in 1450 had page numbering of any type. Professor Baron hypothesizes that the page numbers became common as a guide to printers. It is true that when we would send a job to the printer we included a “layout” detailing the pagination of the different elements of the book: it might look like this:
Clearly the absence of page numbers would make this task much harder.
Professor Baron reports that many of her students have stopped adding page numbers to the papers which they submit to her, and attributes this to their familiarity with the web where page numbers are less common — it’s easier to use “Find” than to wrestle with a location indicator when you’re on-line. I am struggling to remember if I would add page numbers on the essays I had to write when I was an undergraduate. In those days we had to write by hand, so any testimony I could give would probably be irrelevant anyway, as pertaining to the manuscript tradition. But the idea that page numbers are perhaps a fleeting phenomenon, nearing the end of their 500 year life span, is perhaps not altogether ridiculous.