Read mode in Microsoft Word

Some users have reported issues that documents they could previously edit in Word are no longer editable.

After checking document security options and finding no security applied that would prevent editing, it turns out the document had somehow defaulted to opening in Read Mode.

From the ribbon, go to View , then Edit Document .

Once the normal editing tools are restored, the View ribbon will show the usual viewing options on the left side, which usually comprise: Read Mode, Print Layout, Web Layout, as well as Outline and Draft.

Reference:
https://social.technet.microsoft.com/Forums/ie/en-US/8666ac8e-000d-4151-a185-271bc900807c/unable-to-edit-a-word-2016-document-when-loading-an-existing-document?forum=word