Print used to work but for some reason doesn't anymore*. AFAIK "All" and print were the only [legacy] ways to view all posts.
It's not too difficult finding copy-pasters because you can usually tell via their vocabulary and/or sudden change in writing style. A simple google search with a chunk of the post (not all of it, since they can sometimes add some of their own asinine comments and/or other copy-pasted content) will usually do the trick.
*on lengthy threads
The last time I visited one of those threads whilst hunting plagiarists, I just did it the old fashion way, clicking on each page and searching within the thread for suspected copy/pastes. I'm sure there's a much easier way to do it, but frankly after about a week of doing it my will to find these jokers left me. When I'd find one, it'd be like finding a cockroach--where there's one, there are probably a hundred hiding out in random cereal boxes and in the stove. Too much for my sanity, thanks.
Wouldn't it be so nice if average members like you and me didn't have to waste our time searching for these knuckleheads?
Looks like apart from using the old fashion way, going through each page, there is no other choice. Exact copy/paste is easy to spot, google search would do the trick, but some plagiarists do change a couple of words, 90% match and without having all the posts on a single page, it's a bit difficult to get these sloppy text spinners.