This should work it needs pdftk tool ( and ghostscript ).
A simple case:
Step One: Split into individual pages
pdftk clpdf.pdf burst
this produces files pg_0001.pdf, pg_0002.pdf, ... pg_NNNN.pdf, one for each page.
It also produces doc_data.txt which contains page dimensions.
Step Two: Create left and right half pages
pw=`cat doc_data.txt | grep PageMediaDimensions | head -1 | awk '{print $2}'`
ph=`cat doc_data.txt | grep PageMediaDimensions | head -1 | awk '{print $3}'`
w2=$(( pw / 2 ))
w2px=$(( w2*10 ))
hpx=$(( ph*10 ))
for f in pg_[0-9]*.pdf ; do
lf=left_$f
rf=right_$f
gs -o ${lf} -sDEVICE=pdfwrite -g${w2px}x${hpx} -c "<</PageOffset [0 0]>> setpagedevice" -f ${f}
gs -o ${rf} -sDEVICE=pdfwrite -g${w2px}x${hpx} -c "<</PageOffset [-${w2} 0]>> setpagedevice" -f ${f}
done
Step Three: Merge left and right in order to produce newfile.pdf containing single page .pdf.
ls -1 [lr]*_[0-9]*pdf | sort -n -k3 -t_ > fl
pdftk `cat fl` cat output newfile.pdf
A more general case:
The example above assumes all pages are same size. The doc_data.txt file contains size for each split page. If the command
grep PageMediaDimensions <doc_data.txt | sort | uniq | wc -l
does not return 1 then the pages have different dimensions and some
extra logic is needed in Step Two.
If the split is not exactly 50:50 then a better formula than w2=$(( pw / 2 )), used in the example above, is needed.
This second example shows how to handle this more general case.
Step One: split with pdftk as before
Step Two: Now create three files that contain the width and height of each pages and a default for the fraction of the split the left page will use.
grep PageMediaDimensions <doc_data.txt | awk '{print $2}' > pws.txt
grep PageMediaDimensions <doc_data.txt | awk '{print $3}' > phs.txt
grep PageMediaDimensions <doc_data.txt | awk '{print "0.5"}' > lfrac.txt
the file lfrac.txt can be hand edited if information is available
for where to split different pages.
Step Three: Now create left and right split pages, using the different pages sizes and (if edited) different fractional locations for the split.
#!/bin/bash
exec 3<pws.txt
exec 4<phs.txt
exec 5<lfrac.txt
for f in pg_[0-9]*.pdf ; do
read <&3 pwloc
read <&4 phloc
read <&5 lfr
wl=`echo "($lfr)"'*'"$pwloc" | bc -l`;wl=`printf "%0.f" $wl`
wr=$(( pwloc - wl ))
lf=left_$f
rf=right_$f
hpx=$(( phloc*10 ))
w2px=$(( wl*10 ))
gs -o ${lf} -sDEVICE=pdfwrite -g${w2px}x${hpx} -c "<</PageOffset [0 0]>> setpagedevice" -f ${f}
w2px=$(( wr*10 ))
gs -o ${rf} -sDEVICE=pdfwrite -g${w2px}x${hpx} -c "<</PageOffset [-${wl} 0]>> setpagedevice" -f ${f}
done
Step Four: This is the same merge step as in the previous, simpler, example.
ls -1 [lr]*_[0-9]*pdf | sort -n -k3 -t_ > fl
pdftk `cat fl` cat output newfile.pdf
