What FREE document management software for mac is available?

I need something like "DevonThink," without the price. I know there are plenty of free programs out there for doing this - can you give me a hand in finding a good one?

For those of you who are unaware of what document management is, and still want to help, it is a program that allows you to view all sorts of documents (.word, .pdf, etc.) in one database without 4,000 windows. It also helps you to sort and categorize the documents. If any further info is needed, google DevonThink software.
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Document imaging software