What should be the average size of a Flash document while creating a website in Flash?

Answer 1

As big as it needs to be.
If you're at all concerned about dail-up connections, the old advice was to keep the total page size under 60kb. Good luck with that, using flash.
And if your target audience is over 25 years old, please use flash conservatively. The eye-candy is generally considered a frigging waste of bandwidth. It's also a royal pain in the *** if you can't bookmark specific pieces of content.