I absolutely despise protected view in MS-Office since I never open Office files from untrusted sources. If you wish to turn off protected view entirely, the following step-by-step instructions worked at least through Office 2013, and I believe Office 2016. I don't have Office 365 available to experiment with.
Adjusting Protected View Settings in MS-Office Programs
1. ALT+F to open the file tab/menu
2. Hit ‘T’ to open the Options Dialog.
3. Arrow Down until you hit Trust Center
a. Hit TAB until you come to the Trust Center Settings button then activate it.
b. Hit ALT+T which will activate the Trust Center Settings Button.
5. In the Trust Center Settings dialog, use up or down arrow to get to Protected View. I say up or down because you will land on whatever setting the last person who used the Trust Center Settings was on, so Protected View could be above or below where you are. You’ll have to listen until you hit it or reach the end and need to reverse direction.
6. Once on Protected View, hit TAB to throw focus on to the checkboxes related to protected mode. You should exercise additional caution in what you are willing to open as far as what comes to you via e-mail attachments or download from the internet, but if your sources are trusted (you know that they run antivirus programs or are major players with tight security) you will generally be fine. You will want to uncheck the one or more of the following checkboxes, which you should encounter in this order:
a. Enable Protected View for files originating from the Internet
b. Enable Protected View for files located in potentially unsafe locations
c. Enable Protected View for Outlook Attachments.
7. There will be one additional checkbox, Enable data execution protection mode, which should be left checked.--
Brian - Windows 10 Home, 64-Bit, Version 1709, Build 16299 (dot level on request - it changes too often to keep in signature)