Free PDF Accessibility Guide: Tagging & Alt Text Made Easy

Imagine opening a PDF and instantly hearing a clear, logical description of every heading, table, and image—no guesswork, no barriers. That’s what a properly tagged PDF can do, and you can achieve it in minutes without spending any money. Below is a practical, free‑tool workflow that takes you from a plain PDF to an accessible document ready for screen readers.

Why PDF accessibility matters

Three free tools that actually work

1. PDF Accessibility Checker (PAC) 2024

2. LibreOffice Draw

3. Apache PDFBox (command‑line)

import java.io.File;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.graphics.image.PDImageXObject;

public class AddAlt {
    public static void main(String[] args) throws Exception {
        if (args.length != 2) {
            System.err.println("Usage: java AddAlt <input.pdf> <output.pdf>");
            System.exit(1);
        }
        String inputPath = args[0];
        String outputPath = args[1];
        try (PDDocument doc = PDDocument.load(new File(inputPath))) {
            PDImageXObject img = (PDImageXObject) doc.getPage(0).getResources()
                .getXObjectNames().stream()
                .map(name -> doc.getPage(0).getResources().getXObject(name))
                .filter(x -> x instanceof PDImageXObject)
                .findFirst()
                .orElseThrow(() -> new RuntimeException("No image found on first page"));
            img.getCOSObject().setString("Alt", "Diagram of sales growth Q1‑Q4");
            doc.save(outputPath);
        }
    }
}

Run the code with a single command: java -cp pdfbox-app-2.0.30.jar AddAlt input.pdf output.pdf. No licensing fees, no hidden costs.

Step‑by‑step: Turn a plain PDF into an accessible one

• Run the PDF through PAC – Open the file, click *Check Accessibility*, and note every item marked “Missing tag” or “Missing alt text”.
• Open the PDF in LibreOffice Draw – For each missing tag, select the element, right‑click, choose *Properties*, then *Tag as* → *Heading*, *Paragraph*, etc.
• Add alt text to images – Click an image, go to *Properties* → *Alt Text*, and type a concise description (under 125 characters is ideal).
• Export as PDF – Use *File → Export As → Export as PDF*. Make sure the *Export tags* checkbox is ticked.
• Validate again – Run the newly saved file through PAC one more time. All red warnings should be gone.

Quick checklist for the busy professional

When a script is faster than a GUI

#!/bin/bash
for f in *.pdf; do
  java -cp pdfbox-app-2.0.30.jar AddAlt "$f" "output/$f"
 done

The script reads each PDF, applies the same alt description (as defined in the AddAlt Java class), and writes the result to an *output* folder.

Common pitfalls and how to avoid them

Real‑world example

Bottom line