Windows only: We've covered a variety of tools for converting PDF files, but if you need to bulk convert a folder full of them, Zilla PDF to TXT Converter gets the job done quickly.

Aiseesoft PDF Converter which is called the Best PDF Converter tool, packs a PDF to Word Converter, PDF to .txt Converter and PDF to Image Converter. You can easily convert PDF to txt, image, word, ...

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.