Can you legally obtain Boeing maintenance documents?
Everything is available for a price, and you don't need Google's help: You can get the Boeing Maintenance Performance Toolbox right from Boeing if you contact them.



You can also Google around and get PDFs of Boeing maintenance documents but these would be from unofficial/unauthorized sources (at least one Boeing maintenance manual made it onto Wikileaks).  

As Boeing likely holds a copyright on their maintenance documents obtaining them from an unofficial/unauthorized source would be an infringement on that copyright.
More importantly you can't guarantee documents from an unofficial source are correct, current, and unmodified. If you intend to use the document for any aviation purposes (like performing maintenance on an aircraft) you would want to be absolutely certain they are the latest approved revision from Boeing.