This is a losing fight. Even if you spent the time, money, and energy to do it, I can still just take a picture with another device or program on the same computer. There is no way to eliminate it, just security theater that makes it seem like a box was checked to prevent it. Many will do other routes like, convert it to a video or corm package to display images, but this provides typically a worse experience of the document and usually kills a lot of accessibility items which actively harms your users.

Make sure the copyright is well marked, and maybe update your terms of use for the platform so you have a  clear avenue to go after folks if they are caught using.