When we navigate to a page with a .pdf or .docx, instead of the document being rendered in "preview mode", we see spinning circles and the document never renders. Since this is customer facing documentation, this functionality it critical, or at least eliminating the bug/error is critical.
This happens in Chrome, Safari and Firefox browsers.
From your screenshot it appears you are running into an issue being tracked as CLOUD-400, which is presently in an open/unresolved status. However, to confirm and track this behavior please submit a case in your customer group ( MyJive Secret Support Group Administration FAQ ) where a member of our support team can assist in reviewing through your specific instance.