Need an in-browser PDF reader? Sure you could go with Adobe Reader, but who wants that bloated mess? If you want something quick, built in and simple you need to go with the Nodobe add-on for Firefox.
At this time Nodobe support 38 different file format:
doc, docx, rtf, xls, xlsx, ppt, pptx
png, jpg, gif, tif, bmp, ppm, xpm
odt, odf, ott, odg, odp, stw, sxw, std, sxd, sti, sxi, sxc
sda, sdd, sdw, vor
otg, stp, ods, pts
You can pick up the Nodobe Viewer on its official web site or the Firefox Add-ons web site. Free yourself from Adobe, and give it a shot today. Also if you know of anymore Adobe Reader alternatives, be sure to share!