Protecting Storyline files in a WordPress site

Hello, all.

I use Brian Batt's excellent plugin to upload Storyline content (https://www.elearningfreak.com/). The images in the projects are watermarked with a semi-transparent overlay, so there's no concern when the actual SL file is playing.

Does anyone have suggestions for the best WP plugin to ensure that individual files (videos, graphics, etc.) can't be accessed/downloaded?

(Brian outlines how to use the miniOrange option, but at $150, it's too pricey for my liking.)