Sorry, but this is definitely a case where code speaks louder than words. PDF.js was a miracle for its time, and the guys behind it definitely aren't amateurs.

The PDF standard is far richer than the SVG object model, and not to mention SVG performance in just about every browser except for Chrome has always sucked balls.

Using canvas seems a solid trade off - pay upfront with RAM in order to consistently render and cache a page once, or try to jerry-rig some nasty translation to SVG that's painfully slow to zoom or scroll, and no longer renders consistently across browsers.