Adobe 62000112DM User Guide - Page 308

ADOBE ACROBAT 3D VERSION 8 301 User Guide 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 source document's paragraph styles or other struc­ tural information to produce a logical structure tree that 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, and then 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. Though the Add Tags To Document command adequately tags most standard layouts, it cannot always correctly interpret the structure and reading order of complex page elements, such as 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 that cause reading order problems in the PDF. For more information, see "Add tags to an existing PDF" on page 305. 9. Add other accessibility features to the PDF. This stage includes setting the document language, making sure that security settings don't interfere with screen readers, creating accessible links, and adding bookmarks. For more information, see "Set the document language" on page 313, "Prevent security settings from interfering with screen readers" on page 313, "Add accessible links" on page 312, and "About bookmarks" on page 327. 10. Evaluate the PDF and repair tagging problems. Once you have a tagged PDF, you must evaluate the document for reading order problems, tagging errors, and acces­ sibility errors, and then repair them as needed. No matter which method you use to tag the PDF, you'll probably need to 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 as figures. Similarly, the Add Tags To Document command may erroneously tag graphical characters within text-such as drop caps-as figures instead of including them in the tag that represents the rest of 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. You can use this report to guide you as you repair tagging problems. You can identify other tagging, reading order, and accessibility problems for any PDF in Acrobat by using the Full Check tool or the TouchUp Reading Order tool. For more information, see "Check accessibility with Full Check" on page 291 and "Check and correct reading order" on page 307. 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 (as many web pages do), 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 struc­ tured to display all the elements correctly in a browser.