Just installed March 2017 CU for SharePoint 2016. Now users can't open PDFs. When clicked in a library, Adobe Acrobat opens with the error There was an error opening this document. This file cannot be found.
Meanwhile, the browser directs the user to the Word Online which opens the PDF.
If I go directly to the PDF, i.e. http://example.com/sites/site/documents/file.pdf, it opens fine in IE, using whatever IE uses to view PDFs.
It appears the click event in the library is causing a ruckus...
UPDATE
I've since removed the OWA server entirely from the farm (in dev) and now Adobe opens the file alone as expected. Adding it back in since it's def a OWA server issue.
Also tried installing the latest CU for OWA/OOS, but that errors out saying the expected version doesn't exist...