Drupal 7 - How do I update a file that has already been uploaded?

Sometimes files, like images, PDFs and Word DOCXs go out of date.  You can always upload a new file and update your link to the file, but that often changes the URL of the file.  If you don't want the file's URL to change, use this procedure.  Note: Using this option will overwrite the original image or document on Drupal.

1. Login to your Drupal site.
2. Go to Manage > Content > Files.
3. Find the relevant file in the table list of files, and click the "edit" at the end of the row.
4. In the Edit Image or Edit Document page, in the Replace File field, click the Choose button to find and select the new file on your computer.
5. Check the box Keep Original Filename.
6. Click the Save button.

It may take several minutes for the various caches to clear (on Drupal, on your browser, and the Varnish cache).  You can try clearing the cache.