How tags affect reuse and accessibility – Adobe InDesign CS3 User Manual
Page 497
INDESIGN CS3
User Guide
490
When you apply tags to a document for PDF export, the tags do not control which content is exported to PDF, as is
the case with XML export. Instead, the tags give Acrobat more information about the document’s structural contents.
Advantages of using tags
By applying tags to your document before exporting to PDF, you can do the following:
•
Map InDesign paragraph style names to Acrobat tagged Adobe PDF paragraph styles to create a reflowable PDF
file for viewing on handheld devices and other media.
•
Mark and hide printing artifacts, text, and images so that they won’t appear when reflowed in Acrobat. For
example, if you tag a page item as Artifact, the page item will not be displayed when you reflow the contents of a
tagged Adobe PDF document on a handheld device, a small display, or a monitor at a large magnification.
•
Add alternative text to figures so that the text can be read aloud to the visually impaired with screen-reading
software.
•
Replace graphic letters, such as ornate drop-caps, with readable letters.
•
Provide a title for a set of articles, or group stories and figures into articles.
•
Order stories and figures to establish a reading order.
•
Recognize tables, formatted lists, and tables of contents. Recognize which content blocks belong to the different
stories.
•
Include text formatting information such as Unicode values of characters, spacing between words, and the recog-
nition of soft and hard hyphens.
See also
“Structure pane overview” on page 530
How tags affect reuse and accessibility
The content of a Adobe PDF document can be reused for other purposes. For example, you might create an Adobe
PDF file of a report with text, tables, and images, and then use various formats to distribute it: for printing or reading
on a full-sized monitor, for viewing on a handheld device, for reading out loud by a screen reader, and for direct
access through a web browser as HTML pages. The ease and reliability with which you can reuse the content depends
on the underlying logical structure of the document.
To make sure that your Adobe PDF documents can be reused and accessed reliably, you must add tags to them.
Tagging adds an underlying organizational structure, or logical structure tree, to the document. The logical structure
tree refers to the organization of the document’s content, such as title page, chapters, sections, and subsection. It can
indicate the precise reading order and improve navigation—particularly for longer, more complex documents—
without changing the appearance of the PDF document.
For people who are not able to see or decode the visual appearance of documents, assistive technology can access the
content of the document reliably by using the logical structure tree. Most assistive technology depends on this
structure to convey the meaning of content and images in an alternative format, such as sound. In an untagged
document, no such structure exists, and Acrobat must infer a structure, based on the reading order choices in the
preferences. This method is unreliable and often results in page items read in the wrong order or not read at all.