Paul Thurrott brought this tip up in a recent Windows Weekly episode.
This tip is not for Office 365 subscribers. If you acquire and install the desktop Office suite via an Office 365 subscription, you cannot download the software and install it offline. You have to do so via the Office 365 web site. Instead, these downloads are for customers who purchased Office at retail (or online), for Windows or for Mac.
Microsoft currently lets you download the installers for Office 2007, 2010, and 2013 for Windows, for example.
You will need the Office product key which you have purchased in advance.
If this applies to you download your version of Microsoft Office here: https://products.office.com/en-US/download-back-up-restore-microsoft-office-products