So are you able to view content, but pay to download? If that's the case, I could probably write a scraper for the site.
If you have to pay to even see the content, then you may have a bigger problem. Try pooling resources with some of your fellow students, to have one person download all the content, and then make it available to everyone else.
Another option is to expose your instructors. There's a high probability that they are getting kickbacks, especially if this is at college level. Maybe in the form of 10% of each dollar spent by one of their students. Or, they might be getting free equipment or content from Docsity, in exchange for forcing students to use it, and offloading the costs to students.
When I was in college, one of my instructors used these "clickers" that cost students $40 per semester to rent. They used radio to allow submitting realtime quiz answers during class. Students were scored on how many questions they answered, not whether they were correct. If you didn't pay the clicker fee, you lost that 10% of your final grade.
I was suspicious, so I looked into it. It wasn't hard. The clicker manufacturer advertised kickbacks on their own website.