I can’t imagine how I missed the PDF Browser Plug-In for Mac OS X, but thanks to atmasphere for pointing it out. (Background for non-Mac users: while PDF is deeply integrated into Mac OS X, including being the actual print output format, no Mac browser currently displays PDF files in-context—they are all handed off to a second application. Not a big deal, except I can’t count the number of times I’ve clicked on a PDF file and forgotten I downloaded it, and found it days later on my desktop.)