Paid knowledge products have rapidly risen in prevalence and popularity in recent years. Online knowledge platforms have adopted many governance measures to attract more users and protect their needs. We explore the influence of such governance measures on the payment behaviors of knowledge acquirers by constructing a research model based on signal theory. The results show that the characteristic signals of both knowledge products and knowledge providers are positively associated with the number of participants. Authentication marks from the platform do not directly influence knowledge acquirers. The platform authentication marks have a moderating effect by partly replacing the effect of the knowledge providers’ characteristic signals. The results suggest that such authentication measures can help knowledge acquirers identifying high-quality knowledge products and enable them to participate more actively in buying knowledge. Our work has academic as well as practical implications for the operation and management of online knowledge platforms.