Résumé : A challenge for the C2M project is to develop a document workflow for authoring and producing web multimedia documents with a special attention for the aesthetic quality of the final rendering. In this report, we discuss the requirements for advanced multimedia authoring services from a document engineering point of view. Our approach consists in providing a post-editing service to allow authors to adjust their multimedia presentation directly on the final form of the document. The first step of the proposal is to provide a web rendering engine based on the latest advances in web standards. For that purpose, we have developed timesheets.js, a JavaScript library for publishing multimedia web documents. It takes advantage of the new features of the HTML5 and CSS3 web standards and enables synchronization of multimedia contents. The second step consists in designing web-aware authoring tools based on this library, thus providing authors with direct editing services for producing high quality multimedia documents.