Tension Software (www.tensionsoftware.com) has revved Text Converter for OS X to version 1.3. The $9.99 app converts various file formats (PDF, HTML, RTF, RTFD) to standard plain text using drag and drop.
Version 1.3 sport an improved layout. Now all the window area can handle drag and dropping of files. The upgrade has also been optimized for OS X El Capitan.