I guess the Answer is burried in this Document by Microsoft.
https://blogs.technet.microsoft.com/office2010/2009/08/13/protected-view-in-office-2010/
The "protected view" is a winword-process running inside a sandbox (claim by microsoft(. Basically it is an instance of word that has really low privileges. For example it can't change your profile or user settings (which means, that a macro in a word file that is not in protected mode CAN do such stuff... for whatever reasons this might be considered useful in the first place!)
So this winword.exe process has really almost no access rights to anything else on your computer. Hence probably not even to your printers. This seems reasonable as even just exfiltrating your printer names and settings could be a problem.
So to print, the document has to be opened in a winword.exe instance that is NOT sandboxed. It's an "all or nothing approach", which is kinda unfortunate but better than no protection at all.
And yes, that's the price that we have to pay for stupid decisions MS did with early versions of Microsoft office.
1I also hoped to find an answer to this question. It would be useful to print or convert such a scary office doc of unknown origin to PDF.I think it is because Microsoft doesn't know how to protect us from its own document formats. And it has always bothered me that they say trust it if it came from someone you trust. What if someone I used to trust now has a virus which is sending me virus laden documents? Seriously, why can't we go into edit mode get rid of anything "active" and print or export to PDF? – Core – 2017-02-01T01:39:49.403