i see it works in the browser locally but once i build production (cmd >> sencha app build production)
and upload it to my server it does not work. same issue like was mentioend above by 'morphew'
but im not using a local file im using the pdf example you give (http://cdn.mozilla.net/pdfjs/tracemonkey.pdf).
when you build production using the sencha tools it does something to the file(processes/minifies) so i guess taht messes up something. once i remove the pdf.js path out of the SDK folder and out of the app.Json file and add it to the project after production it works great(dont for get to give the html file the correct path to pdf.js)