If the file is protected by DRM (Digital Rights Management) , these tools will not be able to read or convert the content without first removing the protection through authorized means. Getting started with WordToEPUB - The DAISY Consortium
If you want a fast, one-time conversion without installing software, several free web-based tools can handle this: : Supports direct conversion from EPUB to TXT .
: While primarily for creating EPUBs, it is useful if you are working with Word documents that need to be text-accessible. Python Scripting (For Developers)