How to install pdftk

Pdftk is a toolkit for PDF manipulation. It is able to concatenate, shuffle, split and rotate PDF files.

The java port pdftk-java has a native image available. You can install it by modifying the build hook like so:

build: |
chmod +x pdftk

This should give you the binary /app/./pdftk which you can then call in PHP like so system('/app/./pdftk --add --a --bunch --of --params').