Account and Event administrators can download all the uploaded files into a .zip file which can then be unzipped/opened.

Click on 'See All Submissions' in the event dashboard.  Click on the relevant green 'All (question name) Responses (Zip)' button at the top of the screen.  Note that the question name is included on the button.  Therefore, if there are multiple file upload questions in a form, there will be a separate green button for each.

Once clicked, the .zip file will download.