Bash script for reviewing .pdf articles
First of all "bashscript" is a very poor name:


It doesn't tell what the script does. "prepare-articles-for-review.sh" would be better. Or just "prepare-articles.sh"
It is customer to use .sh extension for Bash scripts




If your typical use case is this:


for f in *.pdf; do ./bashscript.sh $f; done 2&gt; /dev/null



Then it would be better to make the script handle multiple file parameters.




  exit $E_BADARGS



I'm not familiar with such variable. I don't think it's a standard, and it's not mentioned in my man bash. If the variable is undefined (and I think it is), then this will have the same effect as exit, which is equivalent to exit $?, where $? is the exit code of the last statement, in this case the echo on the previous line, which is most probably 0. I think you intended to exit with failure, with non-zero exit code.




  NUM=$(pdftk $1 dump_data | grep 'NumberOfPages' | awk '{split($0,a,": "); print a[2]}')



Many problems here:


You should double-quote "$1", to protect from spaces in the filename
The quoting in grep 'NumberOfPages' is redundant
Are you sure there won't be more than one lines matching "NumberOfPages"? Just to be safe, I would add exit in the Awk command
The Awk command can be written simpler as awk -v FS=": " '{print $2}'





  COMMSTR=''



You can simplify to:

  COMMSTR=





  for i in $(seq 1 $NUM);



seq is not recommended because it's not portable. You can achieve the same using native Bash functionality:

for ((i=1; i&lt;=$NUM; i++));





  $(echo "" | ps2pdf -sPAPERSIZE=a4 - pageblanche.pdf)



The $(...) wrapping is really pointless, and awful.
No need for echo "", simply echo is exactly the same.




  $(pdftk A=$1 B=pageblanche.pdf cat $COMMSTR output 'mod_'$1)



Does this work at all? Unfortunately I don't have pdftk so cannot try.
Maybe it's fine, but it looks suspicious.

Btw, you don't need the quotes in 'mod_'$1.
And again, the $(...) wrapping is pointless.




  (pdfnup 'mod_'$1 --nup 2x1 --landscape --outfile 'print_'$1)



As earlier, you don't need those quotes,
and the (...) wrapping is pointless.

The same goes for the rest of the code.

Suggested implementation

I cannot fully test this because I don't have pdftk, but it should work:

#!/bin/bash

if [ $# = 0 ]
then
  echo "Usage: $0 file1.pdf file2.pdf ..."
  exit 1
fi

for file; do
    NUM=$(pdftk "$file" dump_data | awk -v FS=": " '/NumberOfPages/ { print $2; exit }')
    COMMSTR=

    for ((i=1; i&lt;=$NUM; i++)); do COMMSTR="$COMMSTR A$i B1 "; done

    blank=blank.pdf
    ps2pdf -sPAPERSIZE=a4 - $blank &lt; /dev/null
    pdftk A="$file" B=$blank cat $COMMSTR output mod_"$file"
    pdfnup mod_"$file" --nup 2x1 --landscape --outfile print_"$file"
    rm $blank &amp;&amp; rm mod_"$file"
done