Large scale document storage - best practices?

I'm working on re-designing an application that stores a large number of documents.  Projection is somewhere in the 1-2 million additional per year range, for mostly small PDFs (100k or so) and retention is up to 5 years or more.  The documents are currently stored and managed within a Sql Server db - it's functional, but would not have been my choice.  The db backups are difficult at best to manage, nightly jobs are resource intensive, and load is added to a database cluster which (while not impossible) can be difficult and expensive to scale.  However, I have not worked with document storage on a file server on that scale and don't know the limits of scalability there.  I know there are reachable limits on the number of documents and folders where performance begins to degrade, but with a well-organized structure can a file server handle 10 million documents without performance issues?  What is the best practice here?  Management is generally against research into tools ...