Symptoms

In Mozilla Firefox browser, viewing PDF file that is uploaded to a page shows symbols instead of alphabetic characters which are the real content of the PDF file.

Diagnosis

Ensure the Firefox Add-on for Office Connector plugin is installed in the PC that encounters the problem

Cause

The cause hasn't been known yet.

Workaround

Use another PDF Viewer instead of the built-in PDF Viewer by following the instruction in this article.