I doubt it. To further reduce it that much you'll either have to get one hell of a compression tool (winzip won't do a single file and shrink it 75%) or edit the content and if there are images, evaluate they're need or change they're format to a lighter type. If they're BMP's then it will be an easy fix.
thats less than half the file size you started with, what more could you want? anything less would lose layer, color, and other data information. i'm not sure it would work, but if you have embedded BMP files you can try converting them to jpeg. you can also resize the entire document, but you will lose quality. or if the PDF file is simply a picture you can convert it to jpeg which would reduce the size to much less.