Definitely do not tell that friend to head to https://en.m.wikipedia.org/wiki/Z-Library https://en.m.wikipedia.org/wiki/Z-Library and use one of the URLs listed

Definitely do not tell that friend to head to https://en.m.wikipedia.org/wiki/Z-Library https://en.m.wikipedia.org/wiki/Z-Library and use one of the URLs listed there to go to that website and find and download a DRM-free backup copy of all the books they have bought and paid for in the past.