Press "Alt-F2" to open a command line prompt within Unity. Type the command for Evince with your PDF file's name, file extension and its full path relative to the Home directory.

If you want to extract highlighted text from PDF file as a plain text file, then this post covers some good free PDF Highlight Extractor software to do that.

Do you want to open password protected PDF file? This free software can unlock ZIP or PDF file without password free on Windows PC. It works!