I really don't like the look-and-feel of the new pdf.js viewer. On my machine (6 yr old HP running Windows XP with sp 3) it displays slower than Acrobat Reader did, and I was perfectly happy with Acrobat Reader plugin. Frankly I want to disable pdf.js, but haven't been able to figure a way to do it. It doesn't display anywhere I could find on Add-ons Manager. I don't want to be compelled to use a feature that seems to be a performance detriment, at least for me. Mozilla, please rethink this!