A document management system generates and validates online documents. The document management system enables the customization of an online document through various rendering parameters for customizing the appearance of agreement content rendered to a receiving entity. The document management system may validate the rendering parameters of customized online documents to determine a likelihood that the documents are valid. For example, the system may determine a likelihood that an online document generated with prechecked checkbox is invalid. The document management system may recommend custom templates for online documents or modifications to an online document that may increase a likelihood of achieving an originating entity's objective. For example, the document management system can apply a machine-learned model to recommend a target rendering parameter for inclusion that would increase the likelihood of a receiving entity clicking an “Agree” button.