Can you be more specific about your project(?), like target people, contents uploaded, etc… even if generically presented?
Also are you trying to arrive to the most people or just some, and to give the most functions in your documents or not?
Per example: if you want to let your user print all or a part of the document, from the big commercial formats (PDF, Mobipocket, eReader, Microsoft, ePub and Sony) PDF is the unique option designed to let them do so.
This takes us to your main question: “Is there a universally supported format?”
The answer is: no.
So a project is always something that has many steps and to be successful must have to be laid down fully; the format(s) chosen are directly related with the objectives of the project itself, and the reason I put the questions above.