Safari can view PDF files just fine, but for many people the problems start when you go to save the files or print them. The files get corrupted, and you're met with a message that tells you the file is damaged. There is no problem viewing a PDF you already have in either Apple's Preview app or with Adobe Reader. If Safari is involved, however, you are likely to have some issues.
You can try to open the file in Adobe Reader, and you'll get a similar message.
The cause seems to be a problem with Adobe Reader updates. There's a file in your Library/Internet Plug-Ins called 'AdobePDFViewerNPAPI.plugin'. Find it, and trash it. You'll also see a file called 'AdobePDFViewer.plugin'. Don't trash that one, it's fine.
I had this problem on both my Mac laptop and Mac Pro. I checked with a couple of friends and they all had the same problem. Some people have spent a lot of time on the phone with Apple and haven't gotten the problem resolved, as the issue rests with Adobe, not Apple.
Let us know if you've seen this, or if you haven't. Lots of people are affected, but you may not see the problem until you need to view or print that PDF. Saving a PDF link without opening it works fine, but if the document is opened in Safari, and then saved, then the trouble can begin.