I also have this need and have spent a day looking for a solution..to no avail. I did see a hack (shame though) and will post a link to it once I find it again. After spending the entire day looking at solutions, this may be the only way.
Does any one have a solution to this as the default VM "additional file" option does not work for me, and VM simply picks a file on the server such as config.php or some other file. Never the PDF file I needed.