Electronic documents are becoming increasingly popular in various industries and sectors as they provide greater convenience and cost-efficiency than physical documents. PDF is a widely used format for creating and sharing electronic documents, while HTML is commonly used in mobile environments as the foundation for creating web pages displayed on mobile devices, such as smartphones and tablets. HTML is becoming a more critical document format as mobile environments have been raised as the primary communication channel nowadays. However, HTML does not have the standard content integrity feature, and an electronic document based on HTML consists of a set of related files. Therefore, it has a vulnerability in terms of reliable electronic documents. We have proposed Document HTML, a single independent file with extended meta tags, to be a reliable electronic document and Chained Document, a single independent file with a blockchain network to secure content integrity and delivery assurance. In this paper, we improved the definition of Document HTML and researched certified electronic document intermediaries. Additionally, we designed and validated the electronic document distribution service using Enhanced Document HTML for real usability. Moreover, we conducted experimental verification using a tax notification electronic document, which has one of the top distribution volumes in Korea, to confirm how Document HTML provides a content integrity verification feature. Document HTML can be used in an enterprise that must send a reliable electronic document to a customer with an electronic document delivery service provider.