If you are uploading files with special characters, like the Danish Æ, Ø, and Å, accents, etc, you might want to convert those characters to something more machine friendly, as some setups although there are rare today, don’t handle these characters well. In any case, links to media, like a pdf file, looks awful if not converted. File Renaming on upload, takes care of this.
Demo – three images with special characters
Extract from WordPress.org
Have you ever had any problems uploading files with accents and some special characters to WordPress? Probably the answer is yes. This plugin will help you fix this problem by renaming these files on upload. It will either convert these problematic characters or remove them. Besides that, it can improve your SEO adding some relevant info to your filename, like your domain name or the post title your file is attached on.https://wordpress.org/plugins/file-renaming-on-upload/