From the following links you can download each version Office 2016 in English and Greek. Downloads are from Microsoft's official download server: officecdn.microsoft.com.
The files are in the form of IMG images, not ISO. It is for files that you can burn to CD, DVD or USB. To install they need the key product.
The pictures IMGs are not the same as the ISOs that were available on Digital River, but also the “Click-to-Run” instant install versions.
If you need another language let us know in the comments of the post to add it.
Download the images that interest you