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284
USING ACROBAT 9 PRO
Accessibility, tags, and reflow
Tagging during conversion to PDF requires an authoring application that supports tagging in PDF. Tagging during
conversion enables the authoring application to draw from the paragraph styles or other structural information of the
source document to produce a logical structure tree. The logical structure tree reflects an accurate reading order and
appropriate levels of tags. This tagging can more readily interpret the structure of complex layouts, such as embedded
sidebars, closely spaced columns, irregular text alignment, and tables. Tagging during conversion can also properly tag
the links, cross-references, bookmarks, and alternate text (when available) that are in the file.
To tag a PDF in Acrobat, use the Add Tags To Document command. This command works on any untagged PDF,
such as one created with Adobe PDF Printer. Acrobat analyzes the content of the PDF to interpret the individual page
elements, their hierarchical structure, and the intended reading order of each page. Then, it builds a tag tree that
reflects that information. It also creates tags for any links, cross-references, and bookmarks that you added to the
document in Acrobat.
The Add Tags To Document command adequately tags most standard layouts. However, it cannot always correctly
interpret the structure and reading order of complex page elements. These elements include closely spaced columns,
irregular text alignment, nonfillable form fields, and tables that don't have borders. Tagging these pages by using the
Add Tags To Document command can result in improperly combined elements or out-of-sequence tags. These issues
cause reading order problems in the PDF.
For more information, see
"Add tags to an existing
PDF" on page 287.
Evaluate the PDF and repair tagging problems
Once you have a tagged PDF, evaluate the document for reading order problems, tagging errors, and accessibility
errors, and then repair them as needed.
Whichever method you use to tag the PDF, use Acrobat to touch up the tagging and reading order for complex page
layouts or unusual page elements. For example, the Add Tags To Document command can't always distinguish
between instructive figures and decorative page elements such as borders, lines, or background elements. It may
incorrectly tag all of these elements as figures. Similarly, this command may erroneously tag graphical characters
within text—such as drop caps—as figures instead of including them in the tag that represents the text block. Such
errors can clutter the tag tree and complicate the reading order that assistive technology relies on.
If you tag a document from within Acrobat, the application generates an error report after it completes the tagging
process. Use this report as a guide to repair tagging problems. You can identify other tagging, reading order, and
accessibility problems for any PDF by using the Full Check tool or the TouchUp Reading Order tool. For more
information, see
"Check accessibility with Full
Check" on page 274 and
"Check and correct reading
order" on
page 290.
Create a tagged PDF from a web page
A PDF that you create from a web page is only as accessible as the HTML source that it is based on. For example, if the
web page relies on tables for its layout design, the HTML code for the table may not flow in the same logical reading
order as a tagged PDF would require, even though the HTML code is sufficiently structured to display all the elements
correctly in a browser.
Depending on the complexity of the web page, you can do extensive repairs by using the TouchUp Reading Order tool
or editing the tag tree in Acrobat.
Last updated 9/30/2011
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