Why do I get an error when I try to view PDF documents in Office Online?

PDF viewing in Office Online is not included as part of the Cloud Storage Partner Program. We are in the process of deprecating the feature over the coming months, and are not supporting this integration as part of the Cloud Storage Partner Program. We are also deprecating this support for Microsoft products such as OneDrive. OneDrive no longer uses Office Online for PDF viewing.

Much has changed since Office Online originally added PDF viewing support. In particular, most modern browsers have excellent built-in PDF support within the browser, and most mobile devices have excellent native PDF support as well. These industry advances have made the reasons support was originally added obsolete.