Currently Being ModeratedJan 27, 2013 10:24 AM (in response to marypopins)
No version of Pages (including latest v4.3) provides built-in support for line numbers. MS Word (2007+) for Windows was designed with the automatic line number feature built-in via Page setup. For those unfamiliar with how easy MS Word incorporates this feature, here is a one page overview with images.
Here is a link to a 2009 discussion with creative Pages solutions to incorporate line numbers. Also in this historical Apple Support Community discussion is an Apple link with steps to create line numbers in Pages.
The best use of your time (especially if you measure time as money) would be to install Office for Mac 2011. MS Word in that release offers automatic line numbers. Article here.