Are These PDFs Accessible?
The question of whether or not PDFs are sufficiently accessible to be used on the Web has stimulated much debate over the years. There are some who believe there is no place for PDF on the Web; while on the other hand, some argue that PDF is an essential tool for communicating via the Web.
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UPDATE
Please Note: The intention of this article is not to describe how to make an accessible PDF. Rather, I have produced three simple PDF documents with the minimum amount of specific accessibility intervention and I am interested in seeing how easily they can be used by people who use different screen readers and other assistive technologies. Thanks.
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We all know that the there are lousy PDFs on the Web and some are going to be downright inaccessible to many assistive technology users. But, there are also some PDFS, which seem pretty good to me and are not likely to cause many accessibility problems.
When it comes to whether or not a particular technology should be used on the web, I tend to support the WCAG 2.0 approach of technological neutrality. I am not particularly concerned about the technology that is used, rather the way it is used. Just because something is a HTML page, a PDF document or a Flash movie doesn’t automatically mean that it is accessible or inaccessible.
Since I have some spare time, I thought I would prepare three simple PDFs and try to get a few people who use different assistive technologies to use them and hopefully provide some feedback about how accessible they are.
The three PDFs are all derived from simple documents about different Australian birds. The documents were prepared using MS Word 2007 and all use the same Word template. Each document has an image with an alt text and a caption. The Gannet and Swamphen PDFs are just as they were when converted to PDF. With the Pelican PDF, I modified the Tag order using Acrobat 9.0.
- Gannet-word.pdf– produced in Word and converted to PDF using the Word save as PDF option (conversion tool). The Tag for the image (Figure) is at the top of the Tag Tree (i.e. not in the correct place). But the image caption is in the correct position. This PDF contains a simple two column data table.
- Swamphen-acrobat.pdf – produced in Word and converted to PDF with Acrobat 9.0 Pro. Once again the Tag for the image is not in the correct place in the Tag Tree but the caption is.
- Pelican-acrob-mod.pdf – produced in Word and converted using Acrobat. The Tag for the image (Figure) was then moved to the correct position using Acrobat. This PDF contains a data table with 3 columns.
I would like to acknowledge the advice I got from the book “Accessible and Usable PDF Documents” by Karen McCall and the help of Andrew Downie and Russ Weakley in preparing the PDFs.
Please tell me what you think
I would very much like to hear what people think about the accessibility of the different PDF documents. In particular, I am interested in finding out how well different screen readers and refreshable Braille machines present the documents.
Roger,
It’s a solid first attempt at PDF accessibility, however there are a number of issues with your tagging syntax that will prevent less sophisticated screen readers from properly interpreting your content.
What confuses me is why your content structures are set according to PDF accessibility standards, however your Tag structures are not. Did you rename your Tag tree, because that is not how any Distiller or conversion tool will assign a tagging structure.
More than happy to discuss at further detail.
Adam Spencer
Thanks to Adam for his comment and to the others who have contacted me directly with feedback.
I would just like to clarify something, because I think there may be a slight misunderstanding of my intentions. My aim was not to make an example of a perfect accessible PDF. Rather I was interested in seeing if it would be possible for someone who is familiar with Word to make a basic PDF that is accessible without requiring any detailed knowledge of Acrobat or accessibility. To this end, I produced a Word template that included styles for the different levels of document headings, image and table captions, table row and column headers and the footer. As I explain in the article, I converted the bird documents to PDFs in different ways. And, the only time I did anything with the Tags was to reorder the image Tag in the Pelican PDF.
In answer to Adam’s question, I did not rename the Tag Tree or do anything else. I know the TH styles for the data tables are presented as TD in the PDF Tag Tree and I could probably change them, but I decided against this because I am interested to see how accessible the data tables in Gannet and Pelican PDFs are without any direct intervention.
If you have the time, could you please try out the different PDFs with assistive technologies and tell me if you can access the headings, alt text, footers and if you can use the data tables effectively. Thanks.
Hello,
First of all congratulations for this work on these PDF documents.
Unfortunately there are many omissions in these documents.
In Acrobat, the numbering used on the Order navigation panel does not correspond to the reading order but to the order the different content layers on the page overlay each other (used for reflow a PDF). So, when you want to check the reading order of content by a screen reader, the displayed numbering may be inaccurate.
The reading order of a page by a screen reader corresponds to the sequence in which the tags are ordered in the tag tree. To change the reading order of items on a page, you just need to move the tags in the tag tree on the Tags navigation panel. The first tags in the tag tree are the ones which are read first.
For example, on the first page of Gannet-word.pdf, the figure has the number 6 and the legend has the number 7. But, a screen reader reads the picture and then several paragraphs, then only the legend because the tag of legend is not after the figure.
There are also problems on tables, headers are not defined () and the headers are not linked to their cells.
I am working on AcceDe project. One of the objectives of this project was to create free educational guides and manuals for those who want to make their PDF documents accessible. The French AcceDe manuals have been available online since August 2010 : http://www.pdf-accessible.com/Manuels-AcceDe.html
We now aim to publish the English versions by November 2010.
I hope this comment and our manuals will help you.
Regards,
Sébastien Delorme.
AcceDe project.
I misread your article and I see that these problems were voluntary. Sorry for the misunderstanding
I hope, I partially answered your questions on the presentation by screen readers.
As to whether a PDF is accessible or not is affected my many factors. There are plenty of places for information on how to optimise a PDF for accessibility and the web. How good this process is is debatable.
I’ll restrict my comments to a few points rarely mentioned:
1) there is more than one way to generate PDFs and the tool used will affect the outcome.
2) the fonts used will affect the outcome. More and more PDFs aren’t fully searchable, or indexable. Ultimately PDF is a preprint format, not an archival format, so tends to be glyph orientated rather than character orientated.
3) The software used to prepare the original document (in conjunction with fonts) will effect the outcome
4) For some languages, esp. languages written in a complex script languages, it may be impossible to generate accessible PDF files.
Andj.
I have checked out the three PDFs with three screen readers: Window-Eyes v7.2, NVDA 2010_2.rc1 and JAWS V11. Both NVDA and WE report all paragraphs and tables. NVDA and JAWS report the various level headings. JAWS reports tables, but not paragraphs unless headings. Regardless of the level of markup, WE and JAWS can be instructed by the user to announce the top row and/or the left column as headings in conjunction with relevant cells. Tables in these files can therefore be read very effectively. The latest version of NVDA will deal with cells marked as well on HTML pages when using Firefox. Unfortunately, it cannot be instructed by the user to treat cels which the user knows to be headings as such. It therefore only anounces cell locations and cell contents in these files and does not associate headings with relevant cells. I would need to mark up a PDF appropriately to see if it would then announce header cells with their targets. While I may be incorrect, I suspect that no screen reader yet takes advantage of correct table markup in PDFs. All that said, there are vast numbers of HTML tables that are not marked up very well, but I digress.
It amazes me that a clearly written article still managed to be misread! I wonder if there is a branch of pyschology that studies this. I could provide lots of examples where I’ve written an email saying, do not reply to me, reply to xyz. But I still get the replies!
Sorry for that rant and to get back on topic, I like the test. But I’m still none the wiser whether any of them were accessible. I’m assuming from Andrew’s reply that none passed with 100%.
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