custom CMS (Content Managment System) for a static site

Need a Content Management System (CMS) installed onto a pre-made static site. The Content Management System will need to have a WYSIWYG text editor and the ability to add/delete pages. There are also pages with document download links that must be editable. Lastly, there is a page with a list that must be edited in list form. The Admin control panel must be simple and clean, and very secure.