[IceHand]

Here's a little Bash script that will convert all PDFs in the current folder first to PGMs with pdftoppm then run this algorithm on the PGMs, make a small white border around the text (I like to have a small border), crop every images to three overlapping images (it's not exactly what I had in mind in the above post, but it'll work good enough in most cases) and finally convert it back to a new PDF.

Requirements: pi, pdftoppm (part of Poppler and/or Xpdf), ImageMagick (v6.3.2 or newer is needed for the -extent option to work properly), libtiff

#!/bin/bash
set -e

for i in *.pdf; do
	if [ -f "$i" ]
	then
		echo "Converting file \"$i\". Please wait ..."
		PDFName="`basename "$i" .pdf`"
		mkdir "Temp-$PDFName"
		cd "Temp-$PDFName"
		pdftoppm -r 180 -gray "../$i" "$PDFName"

		for i in *.pgm; do
			pi "$i" "New-$i"
			rm "$i"
		done		
		
		for i in *.pgm; do
			convert "$i" +compress -gravity Center -extent "106%x101%" -gravity East -extent "104%x100%" "`basename "$i" .pgm`.tif"
			rm "$i"
		done
		
		for i in *.tif; do
			convert "$i" +compress -gravity North -crop "100%x34%" +repage -depth 8 "`basename "$i" .tif`-1.tif"
			convert "$i" +compress -gravity Center -crop "100%x34%" +repage -depth 8 "`basename "$i" .tif`-2.tif"
			convert "$i" +compress -gravity South -crop "100%x34%" +repage -depth 8 "`basename "$i" .tif`-3.tif"
			rm "$i"
		done
		
		tiffcp *.tif "New-$PDFName.tif"
		
		tiff2pdf -z "New-$PDFName.tif" -o "New-$PDFName.pdf" -t "$PDFName"
		
		rm *.tif
		
		mv "New-$PDFName.pdf" ../
		
		cd ..
		
		rmdir "Temp-$PDFName"
	else
		echo "ERROR: No PDF files found"
		exit 1
	fi
done

echo "Done."
exit 0