I made a script to do that task for me, but I'm afraid it's Linux only. If you have access to a Linux box you can try it.
The script will look for PDFs in the current directory, create an "CYBOOK Converted PDF" folder, optimise the PDFs and put all of the optimised PDFs in the created folder. You'll need to have Ghostscript, ImageMagick, libtiff and GIMP installed. The "batch-unsharp-mask-4.scm" file goes into GIMPs scripts folder.