This is the perfect plugin.

I use this plugin to allow my clients to upload files on their own. I can create a link to a file (on their website) and allow them to just upload a new file (with the same name) and I can automatically have it set to overwrite the old file, this way the link can always remain the same. There are many great options in the Pro version of the plugin, and I highly recommend the Pro version. It’s very affordable and a great deal. I recommend this plugin. And I’ve been using it for years and have never had a problem. ?? – Gary Gordon (WPBNS)