How can I merge PDF files (or PS if not possible) such that every file will begin in a odd page?

Question

I am working on a UNIX system and I\'d like to merge thousands of PDF files into one file in order to print it. I don\'t know how many pages they are in advance.

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Answer 1

The code by @Chris Lercher in https://stackoverflow.com/a/12761103/1369181 did not quite work for me. I do not know whether that is because I am working on Cygwin/mintty. Also, I have to use qpdf instead of pdftk. Here is the code that has worked for me:

#!/bin/bash

for f in *.pdf; do
  npages=$(pdfinfo "$f"|grep 'Pages:'|sed 's/[^0-9]*//g')
  modulo=$(($npages %2))
  if [ $modulo -eq 1 ]; then
    qpdf --empty --pages "$f" "path/to/blank.pdf" -- "aligned_$f"
  else
    cp "$f" "aligned_$f"
  fi
done

Now, all "aligned_" files have even page numbers, and I can join them using qpdf (thanks to https://stackoverflow.com/a/51080927):

qpdf --verbose --empty --pages aligned_* -- all.pdf

And here the useful code from https://unix.stackexchange.com/a/272878 that I have used for creating the blank page:

echo "" | ps2pdf -sPAPERSIZE=a4 - blank.pdf