Operation Manual

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Accessibility, tags, and reflow
Last updated 4/7/2015
Screen readers cannot read document features such as images and interactive form fields unless they have associated
alternate text. Screen readers can read web links; however, you can provide more meaningful descriptions as alternate
text. Alternate text and tool tips can aid many users, including users with learning disabilities.
Fonts that allow characters to be extracted to text (Acrobat Pro DC)
The fonts in an accessible PDF must contain enough information for Acrobat to extract all of the characters to text for
purposes other than displaying text on the screen. Acrobat extracts characters to Unicode text when you read a PDF
with a screen reader or the Read Out Loud feature. Acrobat also extracts characters to Unicode when you save as text
for a braille printer. This extraction fails if Acrobat cannot determine how to map the font to Unicode characters.
Reading order and document structure tags (Acrobat Pro DC)
To read a document’s text and present it in a way that makes sense to the user, a screen reader or other text-to-speech
tool requires a structured document. Document structure tags in a PDF define the reading order and identify headings,
paragraphs, sections, tables, and other page elements.
Interactive form fields (Acrobat Pro DC)
Some PDFs contain forms that a person is to fill out using a computer. To be accessible, form fields must be interactive
to let the user enter values into the form fields.
Navigational aids (Acrobat Pro DC)
Navigational aids in a PDF include links, bookmarks, headings, table of contents, and preset tab order for form fields.
Navigational aids assist users in understanding the document without reading completely through it. Bookmarks are
especially useful and can be created from document headings.
Document language (Acrobat Pro DC)
Specifying the document language in a PDF enables some screen readers to switch to the appropriate language.
Security that doesn’t interfere with assistive software (Acrobat Pro DC)
Some PDF authors restrict users from printing, copying, extracting, adding comments, or editing text. The text of an
accessible PDF must be available to a screen reader. You can use Acrobat to ensure that security settings don’t interfere
with the screen reader’s ability to convert onscreen text to speech.
For more information about PDF accessibility, see www.webaim.org/techniques/acrobat/.
About tags, accessibility, reading order, and reflow
PDF tags are similar in many ways to XML tags. PDF tags indicate document structure: which text is a heading, which
content makes up a section, which text is a bookmark, and so on. A logical structure tree of tags represents the
organizational structure of the document. Therefore, tags indicate the reading order and improve navigation,
particularly for long, complex documents without changing the PDF appearance.
Assistive software determines how to present and interpret the content of the document by using the logical structure
tree. Most assistive software depends on document structure tags to determine the appropriate reading order of text.
Document structure tags let assistive software convey the meaning of images and other content in an alternate format,
such as sound. An untagged document does not have structure information, and Acrobat must infer a structure based
on the Reading Order preference setting. This situation often results in page items being read in the wrong order or not
at all.
Reflowing a document for viewing on the small screen of a mobile device relies on these same document structure tags.
Often, Acrobat tags PDFs when you create them. To determine whether a PDF contains tags, choose File > Properties,
and look at the Tagged PDF value in the Advanced pane of the Description tab.