Originally Posted by Ortep
If we have the same book, page 123 line 5 is exact the same text for us both. You cannot change the layout of a pBook on the fly after it is printed.
The only thing you can say for al books is Chapter 12, section 3, line 5.
Even a slight increase/decrease of the font in an ePUB or Mobi/PRC can 1up entire lines throughout the book.
I kinda like the idea of first word --> last word = page XX of XXX. Maybe using simple <page1>
tags as someone above suggested.