Doesn’t work for my 1200dpi PDF files

I have a number of PDF files in 1200dpi quality. I bought this software hoping it will help to reduce the quality of those files for on-screen viewing. However, I tried all the settings, e.g. "150 dpi - average - grayscale", the file size was reduced only by 0.22%. The output file is still 1200dpi. This software doesnt work according to what it says.

Bat Fung (CA) about PDF Squeezer 3, v3.5.2