Since 2009, the Documentary Heritage of the National Diary Archive (ADN) of Pieve Santo Stefano (Italy) is recognized nationally and internationally as a real "institution" of popular writing. In this context, the PDS (Digital Storytelling Platform) project was born, with the aim of developing a strategy to support the conservation, enhancement and dissemination of the tangible and intangible Cultural Heritage preserved by the ADN, respecting the peculiarities of writing manual and the materiality of its support. The project exploits the new emerging technologies and the cultural skills matured around new media to develop solutions and strategies able to maximize the accessibility, usability and creative reuse of the preserved materials. The ultimate goal is to increase the active participation of stakeholders and citizens in the processes of collection and dissemination of autobiographical testimonies and to encourage the interception of new audiences. This contribution focuses on sharing the PDS experience, drawing attention to the co-design process and the development of a replicable protocol - for the digital dissemination of archival content - which traces all the stages of the work, from user research to the prototyping of the final solution, including the legal aspects related to the protection of privacy and copyright. To design the PDS platform and maximize the dissemination of diary material, without normalizing the singularity of each text and with respect for the authors themselves, human-centered design methodologies and participatory co-design tools were adopted, involving stakeholders and possible new audiences in the design phase, to better respond to their needs and provide a truly useful tool.