Adding remarks to an existing pdf file with pdftk

This is how to solve a special case, when a PDF file is given, but I want to add my remarks in some free space.

The trick is to write the remarks into another single-page pdf file, so that the new text occupies the blank area in the original. In my case, I needed the remark on the second page, so I used the pdftk command-line utility so split the pages into two files, kind-of watermark the second page with my own pdf file and then rejoin them.

The pdftk is free software, and can be downloaded for various platforms here. If you have a fairly sane Linux distribution, you should be able to just grab a package with it (“yum install pdftk” or something).

Surprisingly enough, this was the most elegant solution I could come up with. This is the little bash script I wrote:

#!/bin/bash

tmpfile=tmp-delme-$$

# Split two pages into two files:
pdftk original.pdf cat 1 output $tmpfile-page1.pdf
pdftk original.pdf cat 2 output $tmpfile-page2.pdf

# Add footnote as if it's a watermark
pdftk $tmpfile-page2.pdf stamp footnote.pdf output $tmpfile-marked.pdf

# Recombine the two pages again
pdftk $tmpfile-page1.pdf $tmpfile-marked.pdf cat output original-marked.pdf

# Clean up
rm -f $tmpfile-page1.pdf $tmpfile-page2.pdf $tmpfile-marked.pdf