While redesigning this site, I incorporated a new print style sheet. During the process I discovered a feature in Firefox when printing a web site. Basically, if you have the overflow: hidden CSS attribute set, then it could prevent Firefox from printing all pages from the web site.

So, if you notice that you are only seeing a portion of your web site in your print preview, check your CSS code, and look for any cases where overflow: hidden has been set. For example, I had it set in my container div to allow the footer to always be placed right at the bottom of the page regardless of the content size above it.