PDF thumbnails not showing for all files

Question

Some PDFs don't show thumbnail icons. I have

• checked the setting in Acrobat Reader (DC) and it is set to display thumbnails
• cleared the thumbnail cache using a .bat file
• changed the default reader from Adobe to Foxit
• changed the default reader from Foxit to Adobe
• opened the folder with Adobe > File > Open > large icons. Only one thumbnail shows in the File Open dialog, but THAT thumbnail does not show in Explorer. Other thumbnails that show in Explorer to NOT show in the File > Open dialog in Acrobat Reader.

Still, some files don't show the thumbnail.

With one file that I re-downloaded from the web, the thumbnail shows in the Downloads folder, but when I copy the file to its final destination folder, the thumbnail reverts back to the generic PDF icon of the default reader. When I use the File Open dialog in Foxit or Adobe Reader, the thumbnail shows, then briefly Explorer shows it as well, before it reverts back to the generic icon.

What is at play here? Is this a thing with the file, rather than with Explorer?

I just want ALL pdfs to show thumbnails, not just some, some of the time.

Any ideas?

Edit: Note that I see thumbnails and pdf icons in the same folder. Side by side some files show the PDF icon, others the thumbnail. If I create a new subfolder and copy a PDF that shows with a generic icon into the subfolder, the file shows the thumbnail. But when I navigate away and then back to the folder, the file no longer shows the thumbnail, only the generic icon.

Answer 1

Two possibilities:

• Windows folders have various presets depending on type:

If you set PDF Preview, you might need to change that setting for each folder type in which you keep them (General items, Documents, etc.). After making that setting change, open Windows Explorer for that folder type, select View, Options | Change folder and search options..., and on the View tab of the Folder Options dialog, click Apply to Folders.

Caveat: This setting doesn't always seem to 'stick', in my experience, nor always affect subfolders.

• Another possibility would be that the file is encrypted/password protected... though since you state you can view the contents at first, that is not likely the cause.

Answer 2

I have the same problem and I found a workaround to it, copying the pdf file to another location, renaming the original and then putting back the copy to the original folder. After that you can delete the original pdf.

I've recently migrated from windows 7/32 pro to windows 10/64 pro and haven't see this behavior before in Acrobat Reader XI. This problem looks like a bug in the thumbnail provider library of Acrobat Reader DC.