Dear Roniel,
Allow the user to edit files already added. This is your new requirement. After files are uploaded to your server, you can write code to handle the uploaded files, you can load files to 3rd party tool and edit them. Ajax Uploader is a professional upload tool, it doesn't supply edit functionality. If you want to edit text or html file, you can use cuteeditor for .net, you can refer to demo:
Thank you for asking