Enable PDF previews in Windows Explorer

Open Powershell

Get-ChildItem -Path 'D:\Users\My Folder' -Filter *.pdf -Recurse -File -ErrorAction SilentlyContinue | Unblock-File

 

Ref: 

- https://learn.microsoft.com/en-us/answers/questions/5585306/file-explorer-not-previewing-pdf-files-since-25h2?page=2#answers