When I read PDF files in Chrome, Google Dictionary is not working. But I want to use this when I read PDF books. How can I do this?
i wonder if there is a plugin like this in pdf reader softwares.
I'm not sure it is possible.
Chrome Extensions are usually not designed to access local content [via the file:// identifier]. Since PDF's are downloaded to the temporary cache this problem applies.
The only workaround for this would be to run a local web server and access files via http.
The other problem might be that PDF Viewer (either the one built-in with Chrome or third party like Adobe) are working like plugins therefor the engine running Extensions has only limited access if at all.