The docs show minimum size, maximum size, and allowed file types. I’m not seeing those on my free 4.4.11 version. Are these Pro features?
Yes, they appear to be. The developer is hoping to release a free version of ACF to WordPress early this year, we’ll see, but the new features of the file field will probably be included. Currently only bugs and changed needed to work with WP releases get into 4. If you need these features right away you’ll need to upgrade.