How do I insert a blank page into a PDF with ghostscript or pdftk?

From http://blog.chewearn.com/2008/12/18/rearrange-pdf-pages-with-pdftk/

pdftk A=src.pdf B=blank.pdf cat A1 B1 A2-end output res.pdf

Hope you like this script, just save it as pdfInsertBlankPageAt.sh, add execute permissions, and run.

./pdfInsertBlankPageAt 5 src.pdf res.pdf

#!/bin/bash
if [ $# -ne 3 ]
then
  echo "Usage example: ./pdfInsertBlankPageAt 5 src.pdf res.pdf"
  exit $E_BADARGS
else
  pdftk A=$2 B=blank.pdf cat A1-$(($1-1)) B1 A$1-end output $3
fi 

cat A1 B1 A2-end means that the output file will contain the first page of document A (src.pdf) followed by the first page of document B (blank.pdf) followed by the rest (pages 2 to end) of document B. This operation is called concatenation, Linux cat is very often used to display text, but it is interesting when used with more than one argument.

To create blank.pdf, see How do I create a blank PDF from the command line?