Preview Pane in Network Drive No longer working for Scanned PDFs in 365

Question

Preview Pane in Network Drive No longer working for Scanned PDFs in 365

Kim Wenner 25

Microsoft 365 recently did an upgrade and any scanned PDF's no longer show in the "View Preview Pane". We are scanning 100-300 manual filled out work orders and then having to attach each page to each each different work order orders digitally. By using using the side preview pane it would allow us to see the document to ensure that we are attaching to the correct work order without having to actually open it. This in the past has saved us hours of time and also more ergonomic and less clicking.

Now this preview pane no longer works due to what I am told is a security upgrade. It now says "The file you are attempting to preview will harm your computer. If you trust the file and the source you received it from, open it to view its contents." We have scanned these documents from our own Printer obviously it should be a trusted source.

Our IT dept says there is nothing they can do. There must be something in the background that will allow for our own equipment to be deemed to be a trusted source. Is there not a way where our Scanner/Printer can be trusted when documents are scanned?

Rick Holman 0 Reputation points

2026-02-04T19:59:58.09+00:00
Key Solutions for Network Drive Previews

Trust the Network Location (Recommended):

Open an Office app (Word/Excel) and go to File > Options > Trust Center > Trust Center Settings > Trusted Locations.

Check Allow Trusted Locations on my network.

Click Add new location and enter the network path (e.g., \\Server\Share).

Configure Internet Options:

Press Win + R, type inetcpl.cpl, and go to the Security tab.

Select Local intranet, click Sites, then click Advanced.

Add the network server address (e.g., file://192.168.1.x or file://servername).

Check File Explorer View Options:

In File Explorer, go to the View tab > Options.

Under the View tab in Folder Options, ensure Always show icons, never thumbnails is unchecked.

Ensure Show preview handlers in preview pane is checked.

Remove Problematic Update (If needed):

If the issue persists, uninstall Windows security update KB5066835 via Settings > Windows Update > Update history.

Answer accepted by question author

4 additional answers

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Rick Holman 0 Reputation points

2026-02-04T19:59:58.09+00:00

Key Solutions for Network Drive Previews

Trust the Network Location (Recommended):

Open an Office app (Word/Excel) and go to File > Options > Trust Center > Trust Center Settings > Trusted Locations.

Check Allow Trusted Locations on my network.

Click Add new location and enter the network path (e.g., \\Server\Share).

Configure Internet Options:

Press Win + R, type inetcpl.cpl, and go to the Security tab.

Select Local intranet, click Sites, then click Advanced.

Add the network server address (e.g., file://192.168.1.x or file://servername).

Check File Explorer View Options:

In File Explorer, go to the View tab > Options.

Under the View tab in Folder Options, ensure Always show icons, never thumbnails is unchecked.

Ensure Show preview handlers in preview pane is checked.

Remove Problematic Update (If needed):

If the issue persists, uninstall Windows security update KB5066835 via Settings > Windows Update > Update history.

Answer 1

Good morning Kim Wenner,

Regarding your follow-up questions, adding the folder on your desktop where you store the scanned PDFs to Windows Defender's exclusion list will allow previews to function. The source of the files, whether dragged from email or scanned directly, is irrelevant; only the storage location matters. Scanning directly to a network drive and excluding that folder would achieve the same result. Excluding a folder disables all security checks on its contents, so ensure the folder is secured and used exclusively for scanned documents from your trusted scanner.

I hope you are clear with the information. Should you have any more questions, feel free to leave a message. It's really appreciated of you to accept the answer to help build the community by sharing your experience with the issue. Thanks!

VP

Answer 2

Hi Kim Wenner,

Your IT dept was right, and I'd like to give a short explanation of it to help you imagine more clearly about it. The message you're seeing after the update is part of a new layer of protection in Microsoft 365 and Windows Defender and is supposed to block previewing PDFs that don’t meet certain trust criteria. Unluckily, even PDFs from your own scanner can get flagged if they don’t carry the right digital signature or metadata. Win doesn’t track the source of a PDF the way it does with downloaded files (like from Outlook or the web).

But there's a silver lining. There are ways to make scanned PDFs look like trusted files. But I have to say not all of them are 100% working.

If your scans always land in a specific folder, you can add that folder to Windows Defender’s exclusion list. It’s not perfect, but it reduces the chance of preview blocks.

Or some enterprise-grade scanners (like Ricoh, Canon, or Xerox) can let you embed a digital signature into the PDF during scanning. Even a self-signed cert can help Windows treat the file as more trustworthy.

I hope this piece of advice is useful to you to some extent. If it really is, don't forget to accept the answer so more people would also have a chance to benefit from it too. Thank you :)

Vivian

Kim Wenner 25 Reputation points

2025-11-20T16:39:22.31+00:00

Thank you for your response.

Just for clarification -

When we scan the items - we scan multiples at a time and set our printer to know that after every set # of pages scanned will be a separate PDF File (ie we will scan 100 pieces of paper and it will show up in our emails as 100 separate PDF) then I drag all those PDF's into a folder on my desk top.

Are you saying that I should make that folder a safe spot?

Or are you saying instead of scanning to emailing them that I should set it up so that it scans to the network drive directly and that will make it a safe folder?

Answer 3

VPHAN 20,485 Independent Advisor

Hi Kim Wenner,

Have you found the answer useful? If everything is okay, don't forget to share your experience with the issue by accepting the answer. Happy to help!

Vivian

Answer 4

VPHAN 20,485 Independent Advisor

Good morning Kim Wenner,

Just want to know how it is going with your issue? Should you need more information, feel free to leave a message. Happy to help :)

Vivian

Answer 5

VPHAN 20,485 Independent Advisor

Hi,

How is your issue? If you require more details or assistance, don’t hesitate to send a message. Glad to support you!

VP

THREESALEECERDA 0 Reputation points

2026-01-25T18:10:51.8066667+00:00

Jan 25, 2026. I have the same issue. I cannot view my scanned docs in the preview pane. If it matters I have a Dell laptop, Windows 10, multifunction HP OfficeJet Pro 6978 and ongoing subscription to MSO 365 since 2017. I purchased Best Buy Total Tech (?), but I'd rather start here for guidance. Thanks for extra simple How To instructions, I'm my own IT guy and that's kinda scary!

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Preview Pane in Network Drive No longer working for Scanned PDFs in 365

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