This is a command line application that quickly converts any PDF file into a PDF/A file complete with optical character recognition, meaning you'll be able to search the text.

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.

Jack Wallen shows you how to use the search feature to more efficiently locate the configuration option you need to edit in the nano text editor.