# open PDF files in Firefox

I have Firefox and It was working fine. Recently , I cannot open PDF files even though I have a PDF tools . it start open it and then stuck ... so I have to download all PDF files in order to have a look at . can anyone explain me the problem ??? I have Firefox 25.0.1 and Ubuntu 12.04

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What kind of PDF tool do you want to use? The integrated PDF viewer "pdf.js" is quite good, but there certainly are browser plug-ins from third-party providers. –  David Foerster Dec 5 '13 at 16:48