Yesterday, I wrote about how I am going to use Page-o-Mat to make some Supernote page templates. Page-o-Mat is a python program that lets you describe journals using a YAML based configuration and then generates a PDF. Since template pages are just a PDF, you can use Page-o-Mat for that too.

My first step was to see if I could get ChatGPT to help me. At first, I gave it a link to the docs, but it seemed to have trouble accessing it. So, I just grabbed the YAML for my 2025 journal and pasted it in the chat. Then, I asked what kind of template pages I should make. Its ideas were pretty good and it generated some for me, which worked great.

But, then I asked if it could just make the PDF directly—which it did. On inspection, I see the PDF was generated by https://www.reportlab.com, which says that their “flagship commercial tool for making beautiful PDFs quickly using Report Markup Language and a preprocessor. Create PDFs the same way you create dynamic web pages”. So, it’s essentially (like Page-o-Mat) a language for generating PDFs.

It’s interesting that ChatGPT makes PDF with a language tool even though PDFs themselves are a language. Knowing the internals of PDF, it makes sense. You need to remember the exact byte locations of each object you create to write out the PDF trailer at the end. It’s extremely easy to mess up and there isn’t a good tool for debugging it. Humans would be horrible at making it by hand, and so are LLMs (but we both can make PDFs with tools).