For data in general, I don't think either HTML or PDF is perfect. Both are designed for you to lay out how a document is displayed, rather than the content spec

For data in general, I don't think either HTML or PDF is perfect. Both are designed for you to lay out how a document is displayed, rather than the content specifically. For example, some content in HTML is invisible or split between different divs/spans/whatevers. A lot of it is generated dynamically by JavaScript and async requests. Something like JSON or XML is much more powerful for data storage. For example, you can store the data for graphs as raw data so that the consumer can render the graph however it wants. Display-agnostic data is always more flexible, and I think the best way to provide data on a webpage is both as a visual version and as raw data.