Follow the steps below to enable PDF preview in Firefox.
See steps:
- Go to your browser and click on the Menu -> "Settings" button.
- Go to "Options".
- In the "General" tab, scroll down till you see "Applications".
- When you see your PDF tool there (either Adobe or Nuance, or similar), click on the drop-down arrow on the right-hand side of it, and select "Preview in Firefox".
- Then close the browser down, and re-open it.
- Then, try previewing a PDF in your Outlook web app and see if it works. For me, this fixed my problem.
- If it still doesn't work, try going into your Outlook and looking through your settings there as well.