I love using Pages to create media rich materials. I also own a nice camera that can take very high resolution photos. Combine these two things together and you often end up with gigantic files that are too big to email or, in my case, so big that your office printer spits out a memory error when you try to print.
When you add a photo to a project made with an iWork application(Pages, Keynote, or Numbers) the full resolution version of the image is saved in the document even when you mask or resize the image. This gives you a great amount of flexibility so if you need to enlarge the image later you still have the full resolution version to work with. But when you are finished working on the document you no longer need the full resolution version of the photo, only a version that fits the size that you are using.
Luckily iWork has a built-in feature to help you reduce the size of these documents fast called Reduce File Size. This feature will go through the document and resize any images, trim any video clips, and trim any audio clips that you have inserted into the document with the assumption that they are at the size or duration that you need. In some cases this can significantly reduce the size of the document you are working on. You should only use this feature when you have completed your work on your media inside of the document.
1. When your document is finished and ready to share simply choose File -> Reduce File Size.
2. A window will appear telling you how much space you will be saving.
That's it! Now you'll have a much more manageable document to print and share.