Sorry for reviving an old thread, but I've become pretty obsessed with finding something like Perapera for PDFs and other non-browser uses. I'm going to school in China so I need to consume a lot of Chinese texts and have just found it impossible to look up the words while reading as there are too many class-specific terms that I don't know and not enough time to do a close reading where I look up/learn a lot of the words. I love Perapera and use it constantly, but couldn't find a similar popup dictionary for PDFs: converting PDFs to html or opening them in Chrome doesn't work, either. I tried MDBG and Qtranslate but also found these programs pretty lacking (and in the case of MDBG, way too expensive!).