Apple publishes and makes available for download the very manual linked to. It is in the exact, unaltered form (pdf) as published by Apple and contains all copyright notices as the original. So, as far as that goes, it's fully compliant with copyright legislation.
Perhaps the only possible issue is whether they bothered to ask Apple for permission to post it (ie distribution, under copyright legislation). I'm pretty sure the request would be granted; Apple doesn't typically object to the posting of manuals online.
It's impossible to say whether it's legal or not without contacting Apple and asking them. They are the only people who know what rights they have assigned to which people with reference to which documents.
Copyrights are assignable, and there is no "legal/not legal" test that can be applied just off the top of our heads. There is no government body that checks for compliance. The Police won't come calling if they see a book published on the web, because it's mere existance online offers no proof that any laws were broken.
If the copyright holder (in this case, Apple) said you could post it, you can. If you didn't ask at all, that's a violation of copyright laws, but it is up to Apple to enforce it's rights. Nobody does it for them. The law only enters the picture if Apple brings the law in; the police or the courts can't assess whether it's legal or not by just looking at it anymore than we can.