I love this Workflow but have never yet gotten 'Add file' to work.
I'm running OSX 10.8.3, Evernote 5.0.7, Workflow 6.0 and Alfred 2.0.3 (187).
I've now resorted to using a Finder sidebar folder monitored by Hazel. I just drag a file onto it and Hazel pops it into Evernote.