A 12 page newsletter with lots of photos will inevitably grow to be at least a few mb, you can only minimise that.
1. Trim the photos outside of Pages to be just what you see cropped in Pages
2. Set the resolution to the absolute minimum 72 dpi or 120 dpi for a slightly better appearance
3. Resave them using jpeg2000 and with as great a lossy compression as you think is acceptable
4. A trick used in web pages is to slightly blur the images before jpeg compression and to selectively blur backgrounds.