LLM Guide — ObviousPDF

🤖 LLM Guide

A comprehensive reference designed for coding LLMs (GitHub Copilot, ChatGPT, Claude, etc.) to generate correct, accessible PDFs using ObviousPDF. 📥 Download Markdown

What's Covered

📐 Quick Reference Patterns

Minimal PDF, accessible PDF, and the 10-step accessibility checklist — all as copy-paste-ready code blocks.

🔧 17 Feature Areas

Text, graphics, images, transforms, annotations, forms, bookmarks, page labels, Form XObjects, encryption, signatures, gradients, patterns, layers, associated files, document parts, and colour spaces.

♿ Complete Accessibility Guide

All required steps for PDF/UA: structure trees, alt text, BBox, reading order, artifacts, language, heading hierarchy, table semantics, link structure, and form tooltips.

⚠️ Common Pitfalls

Known mistakes LLMs make: forgetting DisplayDocTitle, mismatched begin/end calls, missing BBox on figures, unbalanced graphics state, and more.

Sample: Minimal Accessible PDF Pattern

From LLM_GUIDE.md — Accessible Pattern

using ObviousPDF;
using ObviousPDF.Accessibility;

var doc = new PdfDocument();
doc.Language = "en-US";           // Required
doc.Info.Title = "My Document";   // Required
doc.DisplayDocTitle = true;       // Required
doc.PdfUaConformance = PdfUaConformanceLevel.PdfUA1;

var root = doc.EnableTaggedPdf();
var sect = root.AddChild(StructureType.Sect);
var h1 = sect.AddChild(StructureType.H1);
var para = sect.AddChild(StructureType.P);

var page = doc.AddPage();
page.AddTaggedText(h1, "Title", 72, 720,
    new PdfTextOptions {
        Font = StandardFont.HelveticaBold,
        FontSize = 24 });
page.AddTaggedText(para, "Body text.", 72, 690);
page.AddArtifactText("Page 1", 285, 30,
    PdfArtifactType.Pagination);

var report = new PdfAccessibilityChecker().Check(doc);
// report.IsFullyCompliant → true ✅

doc.Save("accessible.pdf");

10-Step Accessibility Checklist

#	Step	Code
1	Set document language	`doc.Language = "en-US"`
2	Set title	`doc.Info.Title = "..."`
3	Display title	`doc.DisplayDocTitle = true`
4	Enable tagging	`doc.EnableTaggedPdf()`
5	Tag all content	`AddTaggedText()`, `BeginTaggedContent()`
6	Mark decorative content	`BeginArtifact()`, `AddArtifactText()`
7	Alt text + BBox on figures	`AddChild(Figure, "alt"); fig.BBox = ...`
8	Heading hierarchy H1→H2→H3	No skipping levels
9	Table headers with scope	`AddHeaderCell(scope, id)`
10	Validate	`new PdfAccessibilityChecker().Check(doc)`