What this test checks
This test checks whether the logical reading order in the PDF document matches its visual reading order.
Why this maybe a barrier
For regular users, the reading order of the document is same as the visual order on the screen. For disabled or assistive technology users however, the tabbing order through the document determines the reading or navigation order.
The logical order is the order of elements in the document structure tree.
It is easier for assistive technologies to navigate the document if the logical order matches the navigation order. Otherwise, users relying on assistive technologies may encounter content in a confusing or meaningless sequence. In multi-column layouts or documents with complex elements, this can make comprehension extremely difficult.
WCAG 2.2 Success Criteria
This test is related to multiple WCAG success criteria:
1.3.2 Meaningful Sequence (Level A) — "When the sequence in which content is presented affects its meaning, a correct reading sequence can be programmatically determined."
For more information, visit WCAG 2.2 Success Criteria 1.3.2, under the guideline Adaptable.
2.1.3 Keyboard (No Exception) (Level AAA) — "All functionality of the content is operable through a keyboard interface without requiring specific timings for individual keystrokes."
For more information, visit WCAG 2.2 Success Criteria 2.1.3, under the guideline Keyboard Accessible.
2.4.3 Focus Order (Level A) — "If a Web page can be navigated sequentially and the navigation sequences affect meaning or operation, focusable components receive focus in an order that preserves meaning and operability."
For more information, visit WCAG 2.2 Success Criteria 2.4.3, under the guideline Navigable.
PDF/UA Principle
Section 7.2: Text — "Content shall be tagged in logical reading order. The most semantically appropriate tag shall be used for each logical element in the document content".