Free Password Recovery Software

I'm not aware of any good freeware covering that specific issue, but Passware (http//www.lostpassword.com/) is a reputable commercial provider which offers a very limited trial version of its installed tools. It'll at least give you an idea of how such solutions work.

Passware also offers a 'Software As A Service' solution called Decryptum, which allows you to get a preview of a submitted file for free if it is able to decrypt it (limited class of Word and Excel files) you'll have to pay per use if you actually want a file decrypted and be sure you have the permission of the file owner before submitting their file to Decryptum.

The other big commercial player in the decryption space is AccessData with their PRTK product. There's no evaluation version as far as I know, but you can download the manual and other materials from their website to get an idea of its functionality.

Note that password recovery through brute force methods can be extremely time consuming for Word and Excel files encrypted using stronger forms of encryption that have been available since Office 2003 and the default since Office 2007 unless you have monster hardware at your disposal.

Also be aware (and beware) that there are a lot of dodgy free or cheap password recovery tools out there whose installation may have unintended consequences.

We have some free functionality in OSForensics
http//www.osforensics.com/password-recovery.html
It is limited to single thread in the free software. So finding the passwords can take longer than in the paid for software.