Adobe 62000112DM User Guide - Page 296

ADOBE ACROBAT 3D VERSION 8 289 User Guide Security that doesn't interfere with assistive software Some authors of PDFs restrict users from printing, copying, extracting, adding comments to, 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 a screen reader's ability to convert the on-screen text to speech. See also "Recognize text in scanned documents" on page 68 "Check and correct reading order" on page 307 "Workflow for creating accessible PDF forms" on page 304 "Add alternate text and supplementary information to tags" on page 317 "Set the document language" on page 313 "Prevent security settings from interfering with screen readers" on page 313 "Check accessibility with Full Check" on page 291 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. Thus tags can indicate the precise reading order and improve navigation-particularly for longer, more complex documents-without changing the appearance of the PDF. For people who are unable to see or interpret the visual appearance of a document, assistive software can determine 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 and to convey the meaning of images and other content in an alternate format, such as sound. In an untagged document, there is no such structure information, and Acrobat must infer a structure based on the Reading Order preference setting, which 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. See also "Reading PDFs with reflow and accessibility features" on page 293 "Creating accessible PDFs" on page 299 "Making existing PDFs accessible" on page 305 "Standard PDF tags" on page 319