Yes, it's literally impossible.
@OP
What textbooks are you looking for?
Academic publishing is stranded in an inconvenient era much like the movie and music industry. They don't know that content is easily reproducible and plug their ears and hum whenever someone points the obvious out to them. They try to think that lobbyists and stricter penalties on copyright infringement are going to solve their problems while failing to realize that they are just lobbying for stricter penalties against the people who would otherwise be making them money. They respond with DRM or some stupid firewall. Since this sudden reaction hits mostly no one but actual (or potential) customers, the sudden reduction in ''actual' customers hits their bottom line and they panic.
In reality, a lot of professors now are just publishing their articles on their university websites because they want their articles widely read, and academic publishing is hampering that. The journals that are supposedly the backbone of academia are limited to the few (universities, not individuals) that can pay monthly or yearly subscription fees. It doesn't exactly encourage comment by
anyone. :/
Anyway, I would
love to help you fuck over the broken copyright system! Are you paying $90 for a textbook on calculus?? (which really hasn't changed in hundreds of years) Well, you shouldn't because the authors made up a few problems and change a few variables each year-or-so so that they can make a "new" edition. Yay! You are being fucking ripped off!
So, which textbook are you looking for?