They're not killing PDF.js, just taking a step in a direction that might eventually lead to it dying. This is explicitly mentioned in the ML thread. Shumway ha

They're not killing PDF.js, just taking a step in a direction that might eventually lead to it dying. This is explicitly mentioned in the ML thread. Shumway hasn't been worked on in a while. No idea why, but I would guess that it has something to do with how large the Flash feature set is. Long tail and all that. The reasoning here is probably like so (speculating here): - We want to deprecate most plugin APIs - We still want to support flash - Shumway isn't there yet, let's use pepper flash - Flash and PDF probably need very similar feature sets as far as the API is concerned - Supporting the subset of PPAPI needed for Flash is probably going to let us include PDFium too, which is already supported by Google. As long as we're going down this path, let's try to include PDFium too. - In case PDFium turns out to work, we can decide if pdf.js needs to be replaced I personally hope that pdf.js isn't replaced; since a JS thingy is far better than a vulnerability-ridden C program. At the same time, this depends on how much the demand for a full pdf feature set is.