I assume you’ve arrived at this page because you got an email with a link for our 2011 Christmas letter (which is really the 2012 New Year’s letter now).
Find the PDF at this link.
To download, right-click the link and choose the “save as” option in the drop down menu (exact wording may vary, and I don’t know exactly how a Mac does this). To open in your browser, just click the link as usual. It will open in a new window (or maybe a new tab; I’m not sure).