The CDS is a science driven data centre for reference astronomy data. The objectives have been defined since its creation in 1972: collecting, improving and distributing data for the international astronomical community. However, science and techniques have significantly evolved over the past 50 years, resulting in a deluge of data in terms of both quantity and complexity. The CDS has been able to constantly adapt to these evolutions to offer the community appropriate services and quality data with high added value. In this presentation we will focus mainly on the impact of these changes on the the skills of the CDS data stewards, the so-called documentalists, in terms of specialisation, adaptation to technologies and understanding of data taking into account the evolution of astronomy. All this while ensuring a high level of quality and quick availability of the data.