Any freebie will be illegal (unless it's only a time-limited trial) and almost certainly come with loads of malware.
You don't need Microsoft Office anyway. OpenOffice is just as good, completely safe and totally free:
https://www.openoffice.org/product/index.html
OpenOffice can work with files that have been created in Microsoft Word, Excel, etc and also save files into Microsoft formats. To do so you can either remember to use the 'Save As' command (instead of just 'Save'), and then select a Microsoft format or, far better, change the OpenOffice default so that 'Save' will automatically use Microsoft formats. It's easy to do:
http://helpdeskgeek.com/office-tips/set-openof%EF%AC%81ce-org-to-save-in-microsoft-of%EF%AC%81ce-format-by-default/