Buzz, thoughts, and observations on the ongoing efforts to build information technologies that work for all people at the University of Washington. A blog of the AccessibleWeb@U interest group.
Wednesday, January 28, 2015
Creating Accessible PDFs With Adobe InDesign
AccessibleWeb - Creating Accessible PDFs With Adobe InDesign January 22, 2015, Rick Ells
Making Them Right to Begin With
Making a PDF accessible after it has been created is difficult, sometimes impossible
Use the capabilities of your publishing program to enable it to generate accessible PDFs
What Assistive Technology Needs
Alt text for graphics
The InDesign-to-Accessible-PDF Workflow
Define paragraph styles, including headers
Paragraph Styles mapped to Export Tags
Thread text into a flow
Anchor images in text flow
Give images alt text
Create any bookmarks, table of contents, hyperlinks, or cross-references
Define content order in Articles panel
Add file metadata
In Adobe Acrobat Pro
Set tab order to Use Document Structure
Run Accessibility Check and do further tweaks as needed
The advantage of this workflow is that you are setting up structure, order and alt texts in InDesign, and then simply using that document structure, rather than trying to define that structure in Adobe Acrobat. From personal experience I can say that doing all that in Acrobat is very difficult.
Why InDesign Generated PDFs Are Often Not Very Accessible
InDesign is essentially a graphical layout engine with lots of additional abilities. It is easy to create blocks of text and place graphics, move them around, and create a reasonably good looking layout without thinking about styles, text flow, alt texts or content order. The temptation is to just do the layout, generate the PDF, and go on to the text project.
The steps to improve accessibility of PDFs are just good professional practice for an InDesign user. Defining styles, and applying them as text is entered, ensures consistent presentation of text. Threading text into flows makes it simpler to adjust how text is presented as various layouts are considered.
The hardcopy orientation of InDesign and its very flexibility tempt the designer into layouts that will be difficult to make intelligible with assistive technology. For example, a document layout that has independent text flows breaking across multiple pages is going to be hard to navigate and follow for a person using a voice browser.
Setup Paragraph Styles
Type -> Paragraph Styles brings up the window for defining paragraph styles and group of styles
Clicking on each paragraph style will bring up the Paragraph Style Options, with has menus for setting fonts, spacing, indents, and much more for the style
You can create a paragraph style group by clicking on the little folder icon on the bottom margin of the window. Then you create your styles into that group. Typically, you would define all the styles you expect to use in a project in a group.
At least you should define the following styles: Paragraph, Header 1, Header 2, and Header 3
Set Export Tagging for Each Paragraph Style
For each style, go to Paragraph Style Options -> Export Tagging
Set export tagging for both PDF by selecting the appropriate tag from the drop down list. It would be a good idea to also select the appropriate tag for export to EPUB and HTML at the same time.
Thread Text Blocks Into a Flow
Connect the out port from each text block to the in port of the following text block
Defining the flow helps define the linear structure of the text in the document
Anchor Graphics in the Text Flow
The simplest way to do this to simply drag and drop the graphic into the appropriate location in the text flow
Give Each Graphic Alt Text
Select the graphic, go to Object -> Object Export Options
If the graphic is purely decorative and contains no meaningful content, leave the text field blank for each of the types of alternative text (Alt Text, Tagged PDF, and EPUB and HTML)
If the graphic has meaning, enter the appropriate text in the alternative text field for each type of export.
Export the Document to a PDF File
File -> Export... , then select Save As Type to "Adobe PDF (Interactive)"
Be sure the "Use Structure for Tab Order" option is checked in the Export to Interactive PDF window.
Final Steps in Adobe Acrobat Pro
Set the document language by going to File -> Properties -> Advanced -> Reading Options
Review and tweak the reading order with the TouchUp Reading Order tool at View -> Tools -> Accessibility -> Accessibility right column menu
Penn State: InDesign Accessibility - http://accessibility.psu.edu/indesign