Windows
Download Microsoft Office 2011 SP1 for Mac OS X [Direct Download Links]
Office 2011 is version of the Microsoft Office Productivity Suite for Mac OS. It is comparable to Office 2010 for Windows. Office 2011 for Mac is available in 4 different versions – Home & Student, Home & Business, Academic and Standard.
It includes many similar features to office 2010. In addition, it supports online collaboration tools such as Windows Live SkyDrive and Office Web Apps, allowing Mac and Windows users to simultaneously edit documents over the web.
Since the downloads are from the official download channel of Microsoft, you can be 100% sure to receive virus and malware free setup files. And for the same reason it is absolutely legal and free of charge.
The installation will be limited in nature i.e. trial of 1 month, if done without entering the legally obtained product keys. However if you are willing to first try office 2011 before purchasing it, you can surely run the setup file without entering license keys.