How do I get the pdf preview back without having to unblock one at a time?

To restore PDF preview functionality without unblocking files one at a time, you may need to adjust your settings in Exchange Online PowerShell. Here are the steps you can follow:

1. Download the Exchange Online PowerShell Module if you haven't already.
2. Connect to the module using the appropriate commands.
3. Use the Set-OwaMailboxPolicy cmdlet to update the parameters in the policy. You can set the parameters to allow previews without needing to unblock each file individually. Here’s an example command:

      Set-OwaMailboxPolicy -Identity OwaMailboxPolicy-Default -DirectFileAccessOnPrivateComputersEnabled $false -DirectFileAccessOnPublicComputersEnabled $false
   

4. After applying these settings, test the PDF preview functionality in Outlook Web Access (OWA) to ensure that it works as expected.

This approach should help you regain the ability to preview PDFs without the need to unblock them individually, streamlining your workflow significantly.

References:

• Troubleshooting access and session controls for end-users

Hi Johanna Perri

I completely understand how frustrating this repeated warning and I know how inconvenient it is to unblock PDFs one by one, especially when you work with them constantly. The good news is that you can usually restore PDF previews globally by removing the “Mark of the Web” at the folder level instead of per file. To do this, move your PDFs into a local folder that is not synced to the internet (for example, C:\Users\<YourName>\Documents\TrustedPDFs), then right-click the folder, open Properties, and check under the General tab for an Unblock option. If it appears, unblocking the folder clears the security flags for all files inside it.

Another effective method is to open one PDF in Edge or Adobe Reader and use Save As to re-save it into a trusted folder after that, new files placed there typically preview without warnings. Also, ensure your PDF preview handler is healthy by going to Settings > Apps > Default Apps, selecting your PDF program, and resetting it to defaults. A quick Explorer restart afterward usually brings the preview pane back immediately.

If the issue persists, it may help to repair or reinstall your default PDF application, as damaged preview components can also trigger false alerts. We are continuously improving how Windows handles safe files, so your feedback is truly appreciated. If my guidance helps resolve the issue, please consider clicking “Accept answer” it really helps us improve the support experience 😊.

Let me know if you'd like me to walk you through any of these steps in more detail.