At the heart of papis there is the information file. The info file contains all information about the documents.
It uses the yaml syntax to store information, which is a very human-readable language. It is quite format-free: papis does not assume that any special information should be there.
If you are storing papers with papis, then you most probably would like to store author and title in there like this:
author: Isaac Newton title: Opticks, or a treatise of the reflections refractions, inflections and colours of light files: - document.pdf