Knowledge products are typical experience goods in nature, and the resulting information asymmetry limits the possibility for high-quality vendors to levy high prices. Based on observations of business practices in the age of Internet and digital economy, this paper proposes a novel signaling mechanism where high-quality vendors can be distinguished from low-quality vendors by partially disclosing the content of their knowledge products. The paper portrays and analyzes the conditions under which partial disclosure leads to a separating equilibrium and the related properties.