One of the nice features about Safari is that it displays the PDF files directly in the browser whereas Firefox and Camino will download them and then open them in Preview.
There is a free non-commercial plugin that will allow Firefox or Camino to display PDF files within the browser.
- Download here:
http://www.schubert-it.com/pluginpdf/ - Mount the dmg file
- Copy the .plugin file to /Library/Internet Plug-Ins to use for all users or ~/Library/Internet Plug-Ins to use only for yourself

