Can't prevent Preview from permitting copying content with Adobe Acrobat document security I create educational products and sell at an online marketplace.  I buy clipart and use this.

I create using Pages on my Mac, I then press Print, PDF, open in Preview, grab the thumbnail and combine each page to form a document.  On completion, I export the document to PDF.

I am currently trialling Adobe Acrobat Pro and have followed the steps to secure the document. I have included a screenshot of security options I have set.  I do save the settings and the PDF says by the file name SECURE. I then zip this with another secure file as I need to create my products in US letter and A4 so I zip together and then I upload to the website.

However when I have downloaded I can still lift the clipart.  I have tried this on 3 different Macs and it still can be lifted.  Does Adobe not work with Pages, does zipping affect the security issues or is it that I open on macs and they can override the security settings?

I have read somewhere that the Preview application overrides adobe security settings.  I have not bought Adobe is there another PDF application for Macs that includes security settings I must lock the clipart or I am liable for copyright.
Preview on macOS, like many PDF readers, don't care about these kinds of obscure restrictions on what you can and can't do with PDFs. If you're displaying content to the user, they can copy it, it's as simple as that.

Password protecting the entire file encrypts its contents, and password protecting printing can be followed by PDF readers including Preview, but apart from that all the other restriction types are worthless outside of Adobe Reader.