Users are confused after replacing a file, when the image and thumbs are still teh same after re-uploading.
Add an explanation note on top of the image when returning from [[Special:Upload]].
Just pass &wpForReUpload=1
--------------------------* Goto https://www.mediawiki.org/wiki/File:Bug36380.pdf
**Version**: unspecified download from the File history the lastest version to your computer (just to see that this works)
* create a modified version on your computer
* upload the modified file using https://www.mediawiki.org/w/index.php?title=Special:Upload&wpDestFile=Bug36380.pdf&wpForReUpload=1
After the upload of your changed version you will see that the preview image has NOT changed, and will not show your new version.
**Severity**: enhancementAfter clearing the browser cache with Ctrl-F5, you will see the correct preview image.