Lobo, I did a "Save As Reduced Size PDF" on your No 166 to "Acrobat 10 or later" compatibility and she came down to 12mb from 21mb.
The 200DPI looks OK on 'puter monitor.
I think black and white pages could be scanned in Greyscale to further reduce the size; I've just tried scanning one page as GS then the next as colour and Acrobat didn't complain.