For the site rules, go to the bottom of the page. *Any* page. Look for the word "Rules" in the bar just above all the copyright notices.
Basic policy: EN World does not support copyright infringement - we believe that owners of IP deserve to get paid for their material. This doesn't mean you can't talk about it - if you want to show to the world that you're cheating publishers and designers out of what they've earned, that's on you. But, we don't allow EN World to be used to support trade in such documents. Generally, you can't post them here, nor post direct links, or give instructions on how to find them.
For the specific case, I presume you're talking about the "alpha" of the PHB. Technically speaking, yes, it is covered by copyright. At the moment, we are pretty sure that's not costing WotC a dime in sales. As news and discussion-fodder, it looks a whole lot more like free advertising for the upcoming book. I suspect WotC will *gain* from having it out there, not lose.
If WotC asks us, we'll scrub direct links to it. Going forward, anyone posting such with the message, "Hey, you can use this instead of buying the PHB!!1! Woot!" is likely to get thwapped with a banhammer.