No matter what I try, I cannot view downloaded PDFs in the preview pane.

Question

No matter what I try, I cannot view downloaded PDFs in the preview pane.

Cynthia F 5

I have tried adjusting the settings in Adobe acrobat and also in Windows Explorer but no matter what I do I get the "The file you are attempting to preview could harm your computer....." message. It's driving me crazy since I look at hundreds of files every day. This is seriously slowing down my workflow to have to open each file in a new window to view it. HELP!

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3 answers

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Answer 1

Jennifer 75

How on earth is viewing a file in Explorer/Preview worse than opening the damn thing which we are allowed to do?

This has caused SO MUCH more time in my job as I have to now open hundreds of files every week to do accounts or to check before I send to people and then close them, where as just viewing them on Preview was enough!!

Words fail me!!!

Can't you just add an option in settings for us to be able to chose???? We're not all gullible to scammers you know !!!

Stefan Blom 348.1K Reputation points MVP Volunteer Moderator

2026-07-23T18:47:48.5133333+00:00

@Jennifer

You are not communicating directly with Microsoft here, only with your fellow users. Nobody here knows any details on why Microsoft has made a certain change.

If you right-click the icon for a PDF in File Explorer and click Properties, do you see an option to Unblock the file? Choose that option and confirm with Apply. After you have done that, you may be able to see the preview in File Explorer (you may have to restart File Explorer first).

If you need further assistance from your peers in Q&A, I recommend that you start your own thread. Use the Ask a question option. Good luck.

Answer 2

Hi,

This is not a bug or an issue with your PDF viewer as this is a security update from Microsoft. The update is designed to address a vulnerability where attackers could trick users into downloading files that appear safe but are actually intended to steal credentials. In certain scenarios, even previewing such files could lead to the exposure of sensitive information. To reduce this risk, Microsoft has implemented a change that blocks previews of downloaded files that may contain these types of malicious exploits. For more details about this update and how you can unblock individual files, you can check this article.

If you're sure that the files are safe, you can actually use this PowerShell command to let you unblock all document files in a specific path and allows you to preview them again.

Click taskbar search, type Windows PowerShell
Right-click on it then Run as administrator
Enter this command: Unblock-File -Path "C:\Users\admin\downloads\*.pdf"
Replace the path C:\Users\admin\Downloads with the location where your files are stored. You may do this per folder.
Restart the computer and see if it works.

You may also check other commands from this article:

How to unblock previews in File Explorer

Disclaimer: This is a non-Microsoft site. The information seems reliable, but be careful with ads. Research any product before downloading.

Jennifer 75 Reputation points

2026-07-27T09:24:22.2633333+00:00

Thanks but this didn't work

Just to be clear, in PowerShell, AFTER C:\Windows\system32> you enter

Unblock-File -Path "C:\Users\name\folder\filestobeunblocked"

You keep the spaces and the " righ?

When I did that and entered Enter, it went back to C:\Windows\system32> and I went to the folder and it still won't show.

Where can we report to Microsoft what a stupid idea this is?? How is previewing more risky than opening the files? Which you HAVE to do if you want to see it.

Answer 3

It sounds like you're encountering issues with the PDF preview feature in Windows Explorer. The message "The file you are attempting to preview could harm your computer" may be related to security settings or the way the PDF preview handler is configured.

Here are a few steps you can take to troubleshoot this issue:

Check Windows Explorer Settings: Ensure that the preview pane is enabled in Windows Explorer. Go to the View tab in Windows Explorer and select Preview pane.
PowerToys File Explorer Add-ons: If you have PowerToys installed, make sure the PDF preview feature is enabled. PowerToys enhances the preview capabilities in Windows File Explorer.
Advanced Settings: In Windows File Explorer, go to Options under the View tab and check that Show preview handlers in preview pane is selected.
Security Software: Sometimes, security software can block the preview of certain file types. Check your antivirus or security settings to see if they are preventing the preview.
File Permissions: Ensure that you have the necessary permissions to view the PDF files. If the files are stored on a network location, there may be restrictions in place.

If these steps do not resolve the issue, you may need to consider reinstalling or updating Adobe Acrobat, as it is the native application for viewing PDFs, and compatibility issues may arise if it's outdated.

References: