I think I have cracked the issue of converting scanned images into PDF
using only freeware!
First off get the imagemagick toolset from
www.imagemagick.org
You will also need c42pdf available at
http://c42pdf.ffii.org/
c42pdf will create pdf files from group 4 encoded tiff images (only). To
get to those images use imagemagick convert :
convert -compress group4 <any image file> image.tif
c42pdf image.tif
will create image.pdf. Read the docs to see how to build multi page PDFs.
This has worked for a bunch of files for me so far.
-- hbp