One problem with scanned pdfs is that the size is so bloated. One good solution to compress such files is this one script:
#!/bin/sh
gs -q -dNOPAUSE -dBATCH -dSAFER \
-sDEVICE=pdfwrite \
-dCompatibilityLevel=1.3 \
-dPDFSETTINGS=/screen \
-dEmbedAllFonts=true \
-dSubsetFonts=true \
-dColorImageDownsampleType=/Bicubic \
-dColorImageResolution=120 \
-dGrayImageDownsampleType=/Bicubic \
-dGrayImageResolution=72 \
-dMonoImageDownsampleType=/Bicubic \
-dMonoImageResolution=120 \
-sOutputFile=out.pdf \
$1
Here the compression rate can be changed by tweaking resolution values. I found the above gives a good compression without sacrificing the text quality.
