I want to convert all the .odt
.doc
.xls
.pdf
files to .txt
files.
I want to convert these files to text
OpenOffice has a built-in document converter capable of handling a bunch of formats- take a look at unoconv: http://dag.wieers.com/home-made/unoconv/
That being said, I have had some troubles getting that to work in the past- If you're having trouble, take a look at similar programs for AbiWord (another open source word processor).