In the earlier link, you’re provided a link to download the Foxit thumbnail handler shell extension FoxitThumbnailHndlr_圆4.dll and the second link tells you how to register it. Editor’s note: On the other hand if you’re using Foxit PDF Reader, check out their documentation PDF previews are shown as icons instead of thumbnails in Explorer and then see PDF previews are not shown as thumbnails in File Explorer.
