Design Lead at Forward Partners, Startup Investment, Data driven design, product development and the 'fixer' of startups. Formerly @ Notonthehighstreet, Farfetch, Jaguar Land Rover, Mercedes and Ford
In my personal experience, I believe it is better to serve this as a PDF, since not all users will trust ZIP downloads. And even if you ZIP the PDF, when a user opens that file, it will still open it in browser if that's the way their machine is configured.
Best to stick with true pdf.