Calibre is the open source free ebook management tool that will help you to organize all kinds of ebook and convert any large or small document according to your need.
How to Convert Document to any format?
when you first time open it, you will see one of the user manual book already have there. You can convert this book in any format. such as s AZW, MOBI, PRC, AZW1, TPZ, EPUB, LRF, LRX, RTF, PDF, TXT,MOBI.You know by this software you can convert book,any document as any format. This default ebook is in epub format, so you can convert it in any format like pdf, txt, rtf etc. Just select the book and click convert ebook. At the right top corner you have to choose the format. Lets say you choose txt. Then click OK. It will start conversion. After finishing, open the file from the location where  you saved the calibre for the first time installation file.