By compiling official paperwork, bureaucrats in institutional settings effectively make their clients into the particular “types” of subjects best suited to preestablished institutional interventions. The efficacy of such paperwork stems from bureaucrats’ unspoken—and perhaps unacknowledged—belief in sympathetic magic, or a person's ability to transform another person or object by working on a representation of them (in this case, their institutional case file). The practice of sympathetic magic via official paperwork is particularly pervasive in disciplinary settings, like prisons, where institutional imperatives and cultural biases encourage professionals to substitute documentation for face‐to‐face interactions with their clients. How such magic works in practice becomes evident in an examination of case files belonging to adolescents incarcerated in a Brazilian juvenile prison during the first decade of the 21st century. In this case, each document added to an incarcerated individual's case file contributes to transforming him into an irredeemable criminal. [bureaucracy, magic, documents, documentation, crime, criminalization, prison, Brazil]