The solution provided here still doesn't work for me when dealing with extensionless files. It affects all files that are not .aspx pages including images, word docs and PDF files.
In fact, adding the semi-colon only adds the semi-colon to the end of the URL. Leaving it blank adds the .pdf or whichever extension and provides a 404 error. Adding the ';.pdf' adds that to the end of the URL as well. I am also checking the Redirect Pages to Main Extension box as I don't want to have extensions on the site at all.
Is there any better instruction on how to make this work on files? The current solution breaks all not .aspx files on the site so images and other documents no longer work.