A tag describes what a piece of content is. The order of the tag tree normally guides how a screen reader follows the document structure. A bookmark is a separate shortcut to a location in the file. Bookmarks do not create heading tags, and heading tags do not automatically create bookmarks in every application.
Visual position does not prove reading order. A box at the bottom of a page might appear first in the structure. Content within a tag can also be out of sequence.
A tag tree is a hierarchy. Document can contain a section, that section a heading and paragraph, and a table a row containing several cells. The enclosing element is often called the parent and the elements inside it children. These terms describe relationships in the tree.
Tags also need connections to the correct page content. An H2 with no connection to the visible heading does not make that heading navigable. Content associated with two structural locations may be repeated. A paragraph without a proper structural connection may be missed or handled unexpectedly.
An editor can often highlight the corresponding page content when you select a tag. Use this to understand the connection: start with a simple heading, inspect its following paragraph, then a table cell. Do not infer an object’s meaning merely from its position in a panel.
Document
H1 Report 2026
P Introduction …
H2 Results
P The result …
Table …Before
A Results bookmark exists, but every text block is tagged P.
After
Keep the bookmark and give the section heading an H2 tag.
Why this works The bookmark offers a shortcut. The heading tag also makes the section appear in the assistive technology’s heading list.
Open a bookmark and check its destination. Then navigate using screen reader heading commands. Read several paragraphs after the heading. Readers need both the right entry point and a meaningful continuation.
A PDF has several kinds of order. The tag tree, the order in which page objects were written to the file and the order shown in a particular reading-order panel need not be identical. Checking one panel therefore does not replace testing in the intended reading environment.
Use a two-column page as a test. If the story runs down the left column before continuing in the right, that is the sequence readers should receive. Also check the transition to the next page. A bookmark cannot repair sentences interleaved from two columns; the content order needs correcting.
Bookmarks are especially useful in long documents. Name them after the sections and verify their destinations. “Page 17” names a location; “How to appeal” describes what readers want to find. A visible table of contents is another document component, with its own links that need to work.
Sources
Examples are our own unless stated otherwise. These guides distinguish legal requirements, standards and practical advice. Passing an automated check is not a complete assessment of document accessibility.