The reduction in memory usage seems impressive for large PDFs, but peak usage of 695MiB to display a 14-page pdf [1] still seems like loads of memory. On my machine, a native reader (Foxit) [2] takes ~30MiB.
2. The browser measurement includes the browser's overhead. On my non-retina MBP a freshly started Firefox 30 yields an RSS of 240MB (Preview — the system's default image and PDF viewer — is 16MB and grows to 44MB on opening the Tracemonkey PDF). And that's with just Firebug and the WD toolbar, we've got no idea what manners of extensions or building options OP has. And for reference, opening the Tracemonkey PDF grows Firefox's RSS from 240 to 350MB.
3. The article's measurements includes rendered and cached pages, opening the TraceMonkey PDF grows my Firefox's RSS to 350MB but browsing to the end (and ensuring every page is loaded) ends up with a 480MB RSS, a behaviour which also exists (to a lower extent) on Preview, which grows from 44MB RSS to 85MB (then back down to 62MB)
4. Finally, the article specifically notes that "pdf.js still uses substantially more memory than native PDF viewers."
Also, there's about:memory available in firefox for quite detailed memory break-down.
No. You misunderstand point 1, I'm not saying comparing Firefox to Foxit as PDF viewers is nonsensical[0], I'm saying GP comparing the number he gets on his machine to the numbers provided by OP is not sensible: OP uses 64b Firefox on 64b OSX on an rMBP (the retina part quadrupling the size of the render target if software is compatible) while GP uses unknown bitness Foxit on unknown bitness Windows on unknown hardware.
That's a fractally nonsensical comparison, just about everything which can be changed is changed. A somewhat real comparison would require that GP install a FF33 nightly on his machine and look at what happens there, and only looks at the difference between browser open and browser open + PDF. That would give the browser and PDF.js's overhead over opening PDFs in a native client.
> Also, there's about:memory available in firefox for quite detailed memory break-down.
Which is not what's in OP's graphs, not what GP compares his numbers to, and not relevant to my comment.
[0] although it kind-of is, firefox bundles a PDF viewing utility for convenience, it's not a PDF viewer (unless you're in firefox os maybe?)