I was quoting the article there about JSON/YAML, not making that claim myself. Did you take a look at the article I linked? It shows visual examples of hand-co

I was quoting the article there about JSON/YAML, not making that claim myself. Did you take a look at the article I linked? It shows visual examples of hand-coded PDFs that demonstrate the structural similarities I am talking about. Thanks for the clarification on terminology. I could have been clearer and more precise. I referred to "DOM-like structures" as an analogy for the hierarchical nature of PDF objects, not to claim HTML is DOM. My core point wasn't about the technical definition of markup languages, but about the structural similarity between PDF's object model and hierarchical formats. When coding a PDF document by hand, you work with nested structures using delimiters like "<<" and ">>" that create hierarchical relationships between objects - which has practical parallels to working with nested elements in other formats. The forest vs. trees metaphor was to acknowledge that while PDFs aren't primarily markup formats (the trees), they do share structural characteristics with hierarchical formats (the forest) based on my hands-on experience with manual PDF creation. Hope that helps clarify things a bit.