It seems that only recently Mozilla's guys
started developing PDF.js, an engine for rendering PDF documents using HTML5 and JavaScript, and now they have reached the final stretch. The rendering quality has reached such a level that the developers decided to release an experimental version of the extension for Firefox (
XPI file ).

The interface allows you to zoom and flick through documents, there is a display of reduced copies of pages on the left panel, which, if desired, is removed from the screen. You can open a pdf file from your hard disk in your browser and check the rendering quality.
Note that PDF.js works and looks no worse than rendering PDF in Chrome browser. Documents load quickly, fonts are displayed identical to the original. At the same time, the entire PDF.js code is
fully open , while the module for Google’s PDF is not part of the open source project Chromium.
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According to the developers, PDF rendering directly in the browser is much more convenient for the user, because he will not have to think about installing external PDF viewers, many of which, moreover, do not fully support the important PDF specifications and force them to learn the unusual interface (not the same as in the browser).
Although PDF.js currently supports far from all the exotic PDF functions (see
PDF 1.7 specifications on 1310 pages), you can now open an absolute majority of all PDF documents on the Web in your browser using absolutely free code.