Knowledge Intensive Business Services (KIBS) companies have long been recognised as key players in the modern economy since they positively affect the innovativeness of businesses and societies. Their business activities are mainly based on knowledge, which is both the input and the output of their production processes. Despite their small average size, the vast majority of KIBS companies are aware that knowledge is their most crucial competitive resource. However, they often manage their cognitive assets in a substantially informal and undeliberate way. Indeed, such companies face difficulties and obstacles typically associated with a limited size, such as, e.g., scarcity of human and financial resources, lack of time, and short-term orientation. Furthermore, KIBS SMEs face specific challenges, mainly caused by the intangible and knowledge-intensive nature of their business processes. A key issue concerns knowledge documentation and storage, which is essential to make the retrieval and reuse of possessed knowledge easier for existing and newly hired employees. In spite of the above, research about how small and medium sized KIBS companies manage knowledge documentation and storage processes is still limited. To help fill this gap, this paper examines the main difficulties that KIBS SMEs face when documenting and storing their knowledge and how they try to face and overcome these difficulties. In particular, the paper illustrates and discusses the findings of an empirical investigation that involved 13 Italian KIBS SMEs belonging to different sectors. The decision to adopt a multiple case study approach was induced by the exploratory nature of the research. The study revealed that knowledge documentation and storage is a widespread activity among the investigated companies, which confirms the relevance of these processes. The investigated companies are aware that poor documentation generates several problems that result in late responding to client requests. Furthermore, the study allowed identifying some shared challenges that concern the entire document and storage process, as well as collecting useful indications about how companies deal with them. The study has the usual limitations of a case study methodology, and especially the difficult generalisation of the results. This paves the way for future research devoted to confirm what emerged from the present analysis, for example, by means of surveys.