I\'m developing a multilingual web site and the localization is done mostly by using .resx files. But now I need to enable users with some permissions to edit resource files
Best thing you can do is move to a DB driven approach.
Rick Strahl has this excellent article: Creating a Data Driven ASP.NET Localization Resource Provider and Editor with free source code!
It even has a Import feature so you don't have to re-translate the work done so far.
Edit: if you insist on editing the XML files, this article may help: Updatable ASP.NET ResX Resource Provider – yes, it’s possible!