When you upload files, eZ Publish should wash filenames the same way it washes url_alias.

ie:

/nor/content/download/477/2744/file/Døves Tidsskrift nummer 1 2007.pdf

1. Norwegian charters shouldn't be there
2. Spaces shouldn't be there

While on it, filenames should also be shortened, like max 30 letters

There are two reasons that this is important:
1. xhtml validation
2. Users that use older / other browser might not understand the local signs and give a warning

Steps to reproduce

Upload pdf file or probably any other file.