Office Word - Borders not printing.
Office 2016 Word prints, but not borders. Borders show in Print Preview. OS 10.13.3.
null-OTHER, macOS High Sierra (10.13.3), Office Word 2016
Just because something looks right in Print Preview does not mean that the printer won't crop that border because your document margins are larger than what the printer hardware is capable of printing. This might be a call for scale to fit paper size.
Have you explored this further with the Microsoft Word 2016 for Mac forum?