To better compress my personal preference is
pdftops -paper A4 -expand -level3 file.pdf # I'm from EU, so A4 is my common paper format
ps2pdf14 -dEmbedAllFonts=true \
-dUseFlateCompression=true \
-dOptimize=true \
-dProcessColorModel=/DeviceRGB \
-r72 \
-dDownsampleGrayImages=true \
-dGrayImageResolution=150 \
-dAutoFilterGrayImages=false \
-dGrayImageDownsampleType=/Bicubic \
-dDownsampleMonoImages=true \
-dMonoImageResolution=150 \
-dMonoImageDownsampleType=/Subsample \
-dDownsampleColorImages=true \
-dColorImageResolution=150 \
-dAutoFilterColorImages=false \
-dColorImageDownsampleType=/Bicubic \
-dPDFSETTINGS=/ebook \
-dNOSAFER \
-dALLOWPSTRANSPARENCY \
-dShowAnnots=false \
file.ps compressed.pdf
If you do `-dEmbedAllFonts=true` then probably `-dSubsetFonts=true` would also be useful.
And for the rest, `-dPDFSETTINGS=/ebook` should already have most of the values that you set explicitely.