SOftware to convert PDF files to txt.

Dear everybody, what I have is a bunch of PDF files. How can I convert them to txt files? Is there a reliable software or sth? Thanx you if you can share your informaton.
AntFile Converter or ABBYY,the latter is much more helpful, but it's time-consuming and not free. And, both of the software will have gibberish, you have to correct them by yourself.