PDF Tools for TOC

https://github.com/Krasjet/pdf.tocgen

$ pdfxmeta -p 10 -a 1 gabi41.pdf INTRODUCTION >> recipe.toml
$ pdfxmeta -p 11 -a 2 gabi41.pdf "System V Application Binary Interface" >> recipe.toml
$ pdfxmeta -p 12 -a 3 gabi41.pdf "Conformance Rule" >> recipe.toml
$ pdftocgen -r recipe.toml -o toc -v gabi41.pdf
$ pdftocio -t toc gabi41.pdf