Acrobat Chapter 1: Introduction
- Daniel LaGrow
Instructions
Section 1.1: What are Tags?
Tags are invisible markers that carry essential information about elements within a document. They are crucial for assistive technologies like screen readers, which rely on this information to interpret and convey the content. For instance, a screen reader needs to know whether an element is a paragraph, image, or a table. Screen readers cannot determine this unless the element is explicitly tagged.
Tags provide the semantic structure that describes the content and organization of a document. This structure is communicated to assistive technologies, which in turn make it accessible to users. When every element in a document has a clear semantic meaning, screen reader users can understand its organization and navigate it effectively.
For example, sighted users can visually scan a document and move from one heading to another, even if the headings are not correctly tagged. However, screen reader users depend on these headings being explicitly and semantically tagged to recognize them as such. Proper tagging allows screen reader users to easily jump from heading to heading.
Tagging a PDF is arguably the most critical step in ensuring its accessibility. If you are familiar with HTML, PDF tagging will feel familiar since the principles are similar. If you are new to this, a bit of practice will help you become comfortable with the process.
Types of Tags in Acrobat:
Article
Annotation
Bibliography
Block Quote
Caption
Code
Division
Document
Figure
Form
Formula
Heading
Heading Level 1-6
Index
Label
Link
List
List Item
List Item Body
Note
Paragraph
Part
Quote
Reference
Section
Span
Table
Table Data Cell
Table Header Cell
Table of Contents
Table of Contents Item
Table Row
Section 1.2: Remediation Flow in PDF Documents
If you have the original source document:
Optimize the original source document for accessibility.
Convert the source document into a tagged PDF.
Include metadata.
Add or adjust tags as needed.
Refine the reading order and tab order.
Verify the accessibility of your work.
If you need to work with a poorly tagged PDF:
Add metadata.
Create or refine the tags.
Adjust the reading order and tab order.
Check the accessibility of your work.
If the tags are in very bad shape, you might find it easier simply to delete them all and start tagging from scratch.
If you need to start with an untagged PDF:
Add metadata.
For very simple documents, use Acrobat Pro to auto generate tags.
For more complex documents, manually create the tags.
Refine and adjust the tags as needed.
Optimize the reading order and tab order.
Evaluate the accessibility of your work.
If starting with a paper or scanned document:
Scan the document, if needed.
Use optical character recognition (OCR) to generate searchable text.
Proceed with the steps for working with an untagged PDF.
Section 1.3: PDF Accessibility Standards
WCAG (Web Content Accessibility Guidelines) provides rules for making web content accessible. It includes 78 measurable criteria with clear pass/fail outcomes to help authors create accessible content. For example, text must meet a minimum color contrast ratio against its background. If it doesn’t, it fails that criterion. WCAG defines technical requirements (success criteria), techniques for achieving them, and additional guidance.
PDF/UA (PDF/Universal Accessibility), also known as ISO 14289, sets technical standards for accessible PDF documents, based on WCAG 2.0 principles. Like WCAG, it includes specific criteria for accessibility. Shortly after its release, the Matterhorn Protocol was created to help software developers, authors, and editors comply with PDF/UA. It lists 31 checkpoints and 136 failure conditions detailing how a document can fail PDF/UA standards.
Both WCAG and PDF/UA have significant overlap but serve slightly different purposes. Approved by the International Organization for Standardization (ISO), they share the common goal of creating an accessible user experience.