html5 can replace flash, check this link on how firefox can replace flash
still not perfect, but getting better. it will replace flash, just like PDF.js can replace PDF plugins in browsers
I gleefully support the goals of the project.
And yet I regret to report that from my work-related test cases, PDF.js is badly broken with long technical documents with diagrams.
For those who don't know, you can disable it!
1. Type about:config in the address bar and press Enter.
2. Press the big button to bypass the warning.
3. In the Filter bar, paste pdfjs.disabled
4. In the search results, double-click pdfjs.disabled to set its value to true
5. Restart Firefox for the changes to take effect.