Adobe acrobat 7.0.5 sdk 用户手册

Acrobat and the Acrobat SDK provide extensive support for accessibility of documents to 
visually-impaired users. 

This chapter consists of the following sections:

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To enable proper vocalization, either through a screen reader or by some more direct 
invocation of a text-to-speech engine, PDF supports the following features:

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Specifying the natural language used for text in a PDF document—for example, as 
English or Spanish 

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Providing textual descriptions for images or other items that do not translate naturally 
into text, or replacement text for content that does translate into text but is represented 
in a nonstandard way (such as with a ligature or illuminated character)

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Specifying the expansion of abbreviations or acronyms 

The core of this support lies in the ability to determine the logical order of content in a PDF 
document, independently of the content’s appearance or layout, through logical structure 
and tagged PDF documents (see 

). Tagged 

PDF documents are created using the Acrobat Professional user interface or using the 
Acrobat SDK.

An accessibility application can extract the content of a document for presentation to a 
disabled user by traversing the structure hierarchy and presenting the contents of each 
node. For this reason, producers of PDF files must ensure that all information in a document 
is reachable via the structure hierarchy, and they are strongly encouraged to use the 
facilities described in this section.

Additional guidelines for accessibility support of content published on the World Wide 
Web can be found in the World Wide Web Consortium document 

 and its associated documents.

For complete details on accessibility support in PDF files, see the PDF Reference.