Anyone using document management software?

[crypt0m4nia]

Hey all!

I'm dealing with lots of scanning and file organization at work (I'm also in charge of sending/clearing invoices), and things can get messy sometimes. We are using a rudimentary system of grouping the files that somewhat helps me keep everything in check, but I'm sure there's better software online. I'm looking for something that will automatically group PDFs by their content, and also allow me to edit them later on.

I should also specify that I'm not looking for a free app, I'll much rather pay a fair price to be able to reach customer support if something goes wrong.
So, has anyone got some hands-on experience?

Thanks!