I have been reading many posts about the Windows Explorer (Windows 10) not showing previews of .PDF documents. My WE stopped showing .PDFs recently and I needed a solution but all that is typically offered is associating the .PDF files with Acrobat using the "Open With" function after right clicking a file. Also frequently offered is the "Enable PDF thumbnail previews in Windows Explorer" checkbox in the Acrobat "Edit", "Preferences", "General" settings dialog box. Neither worked for me.
I also tried to repair the Adobe Acrobat installation by uninstalling and re-installing Adobe Acrobat. This did not fix the issue.
Going to the administrator account on my laptop did show the .PDF previews so I decided to check my typical user account settings. I normally use a "User" and not the "Administrator" account to provide a small layer of safety to my computing.
Here is how I fixed the issue:
I went to the C:\Program Files (x86)\Adobe\Acrobat Reader DC\Reader\AcroRd32.exe file in Windows Explorer and right clicked the file. I went to the "Compatibility" Tab and clicked on the "Run compatibility troubleshooter" button. This process set the compatibility mode to "Windows 8". I also clicked on the "Security" tab and edited my "User" account to have "Full Control" by clicking the "Edit" button while my User account was highlighted.
.PDF files started showing up in my Windows Explorer preview window immediately.
Hope this is helpful.