generate a list of addresses of matching positions on the device with the
filesystem containing the deleted file. if they're in hex, enclose them in
$(()) to make bash un-hex it before giving it to dd, which doesn't like hex.

for i in `cat pdfpositions `; do dd if=/dev/sda2 bs=1 skip=$(($i)) of=test.pdf count=200K; xpdf test.pdf; read; done