Tips for starting a indesign document: Choosing category, present and size (web or print)

Hei guys!

I got a quite a task on work for creating a publiv document for the municipality I working for. 
Athlough I been working with InDesign before I really dont know much about the "basic steps" which might be cruical for how this final product will end up showing and be used.

The first and most inportant question is whether to choose a print or web category. I know that this public document will mostly be read on screen, but I also know that many people will want to print it to read it on paper and that a A3 (landscape) format probably would be best for a print version to make it easy and readable. 

However, my capacity is limited so I doubt I can make to seperate versions, one for web/pdf and another one for print (A3?). Do you guys have any tips for compromises for this kind of dilemmas for what category/preset/size that can do "all" or do I have to ask the leader of the project what she want to chose;

PDF or a print document/paper?

Just to say a bit on the actuall project; the project is a bout comparing data/information for several small places in the municipality and will consist of pictures, and graphs and diagrams comparing this six places for differences in demographics, maps and so on, but not all comparing information will have to stand next to each other on each page, but some kind of landscape format will probably do best overall.

Sorry if this got messy, just ask for more specific information and I will require my leader also.

Thanks!