If you want to see the size of the photo in Aperture, go to the Metadata view. It will give pixel dimensions and file size. If it does not, you can choose those things to be shown.
To get a photo out of Aperture, you can Export it instead of dragging it out. When exporting you can choose original size or a variety of other sizes.
Or you can choose to have full size high quality previews ("Don't limit" the size and put the quality slider near the high end). If that is your choice, you can drag the preview and get a full size export. I believe you will need to regenerate previews for those images that have already been imported. Full size previews take a lot more disk space.
I believe that apps that have the media browser (Pages, iMovie, etc) use the preview image. So if you want them to have access to the full size image via the media browser, the preview will have to be full size. If I am wrong on this, someone will hopefully correct me.