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Yes. The ExThumbnail component is able to preview any type of file that your Windows Explorer can. If you can not see the file's thumbnail in your Windows Explorer, you can not see it also in the ExThumbnail component. Shortly, the Windows Explorer uses a shell-extension to preview a specific type of file. Shell Extensions are in-process COM objects which extend the abilities of Windows operating system. Most shell extensions are automatically installed by the operating system, but there are also many other applications that install additional shell extension components.

In order to preview PDF files you must:

• install the Adobe Acrobat Reader application,
• check the "Enable PDF thumbnail previews in Windows Explorer", from Edit\Preferences...\General tab of Adobe Acrobat Reader
• .PDF's default viewer is Adobe Acrobat Reader app ( SHIFT + right-click the PDF file in Windows Explorer, Open with, Choose another app, and select Adobe Acrobat Reader (ensure that the "Always uses this app to open .pdf files") )

Without these options the preview of a .pdf file looks as follow: 

With these options the preview of a .pdf file looks as follow: 

The most common reason for not seeing PDF thumbnails is that the Adobe Shell Extension is not properly registered or enabled. This can happen due to various reasons, such as a corrupted installation, conflicts with other shell extensions, or issues with 32 or 64-bit Windows environments. For instance, you are using the 32-bit version of the ExThumbnail control on a 64-bit Windows system, but the Adobe Shell Extension is not installed or properly registered for 32-bit applications.

Adobe Acrobat and Reader include a 32-bit PDF Shell component that allows Windows Explorer to display PDF thumbnails and previews, supported on both 32-bit and 64-bit Windows. This feature is often off by default, but can be enabled in Preferences under General > Enable PDF thumbnail previews in Windows Explorer.

Key Details for Adobe Shell Extension:

• Enable Thumbnails/Preview: Open Acrobat/Reader, go to Menu > Preferences > General, and check "Enable PDF thumbnail previews in Windows Explorer". A re-installation or repair via the Control Panel may be needed if this option is missing
• 32-bit vs 64-bit Windows: On 64-bit Windows, 64-bit Explorer requires 64-bit shell extensions, but Acrobat typically installs the necessary 32-bit/64-bit handlers automatically to make thumbnails work
• Fixing Missing Previews: If thumbnails do not appear, you can re-register the DLL using the command regsvr32 "C:\Program Files\Adobe\Acrobat DC\Acrobat\AcroPDF.dll" (path varies by version) or use ShellExView to check for conflicts
• Conflict Resolution: If you face "Internal Error" messages, this can happen if the 32-bit plugin conflicts with 64-bit Windows 7-11 environments. In such cases, uninstalling the version of Adobe Acrobat Reader and re-installing the version can resolve the issue

If the thumbnail extension still fails, consider repairing your Adobe installation through the Windows Control Panel, which often restores the necessary registry keys for the shell extension.