When you upload media files to Marketo you are creating a static copy on the server. If you later change the file, you have to replace the copy to reflect the change. A more flexible alternative would be to link to the master file stored within your organization (assuming it is publicly available, in our case these documents are in a public Box folder. I know you can import files into Marketo from Box but can you create an inventoried URL that will point to master document instead? Assuming that the latest and greatest version retains the same name and location, the link will always be current.
Basically, an integration similar to video hosting integrations.
Thanks!