Adobe Acrobat 7 Professional - Manual (Page 364)

Elements of accessible Adobe PDF documents
When you create Adobe PDF documents or adapt existing documents for accessibility,
you'll want to consider the following factors:
Reading order
To effectively read information on a page, a screen reader or Text-to-Speech requires that
content be structured. Adding tags to an Adobe PDF document structures the content; it
identifies headings, paragraphs, sections, tables, and other page elements and defines the
intended reading order of the page. (See
Tagging Adobe PDF documents for accessibility .)
After you add tags to a document, you can check the reading order and correct any
problems by using the TouchUp Reading Order tool. (See
Checking a document's reading
order .)
Descriptions for images, form fields, and links
Document features such as illustrations, graphs, and interactive form fields can't be read
by a screen reader unless they contain alternate text that provides a description. And while
web links are read by screen readers, authors can provide more a meaningful name in a
description.
Authors can add alternate text or tool tips to tagged PDF documents that describe these
features to readers with visual or learning disabilities. (See
Checking and adding alternate
text to figures and Making Adobe PDF forms accessible .)
Note: A PDF document that is created by scanning a printed page is inherently
inaccessible because the document is an image, not text that can be tagged into a logical
document structure or reading order.
To convert the text in a scanned PDF document to searchable text, see Converting image-
only scanned pages to searchable text, or learn more about Adobe Paper Capture on the
Adobe website at
www.adobe.com.
Navigation
Navigational aids in PDF documents, such as links, bookmarks, headings, and a table of
contents, provide an easy way for users to go directly to the section they want. Bookmarks
are especially useful and can be created from document headings. (See
Creating
bookmarks and Creating links .)
Document language
The Full Check feature returns an error if a document language isn't specified. (See
Adding supplementary information to tags .)
Security
You can maintain accessibility in a PDF document while restricting users from printing,
copying, extracting, commenting, or editing text. To make PDF documents with added
security features more readable for screen readers, specify a low or high encryption level
when you select a security method in the Document Properties.
For low encryption level security, select Enable Copying Of Text, Images, And Other
Content in the Password Security - Settings dialog box; for high encryption level security,
select Enable Text Access For Screen Reader Devices For The Visually Impaired. (See
Password security options .)