Testing publications with NVDA – PDFs
[Narrator:] NVDA is an excellent tool to use when testing PDFs for accessibility. For this purpose, both Adobe Acrobat Reader and Acrobat Pro can be used. In addition to the initial settings explained in the Configuration chapter, we need to configure NVDA to optimise it for our use.
- Our demo document presents content in four languages. Therefore, we have to download the voices for these languages as Windows OneCore voices.
- Instead of hearing the speech output, for testing purposes we prefer to read it. This can make the search for an accessibility problem easier. We therefore have to activate the Speech Viewer.
- As we find it rather challenging to follow a purely auditory interface, we activate the Visual Highlight so we can see the position of the system focus and the review cursor.
- We activate the reading of all document elements in the Document Formatting settings.
If you have any questions on how to configure one of these settings, please review the previous chapter, Testing publications with NVDA – Configuration.
Accessibility settings in Adobe Acrobat Reader
For our demo, we are going to use Adobe Acrobat Reader, which provides a set of accessibility settings. When Acrobat Reader starts up for the first time while NVDA is running, the Accessibility Setup Assistant will appear. It offers a rich set of options for configuration. To continue with our tour, we select Set all accessibility options, and click Use recommended settings and skip setup. A user can always get this dialogue back using the main menu selection: Edit, Accessibility and Setup Assistant.
If you want to fine-tune and modify settings you may have missed, it is possible to reach the same options here in the Preferences. Open them by selecting Edit and Preferences. Select the Documents panel and deactivate the option Automatically save document changes to temporary file every X minutes. Each time a PDF is saved, the screen reader must reload the document, which can result in a very annoying experience for the user.
We select the Accessibility panel. The first part of the dialogue offers options to replace document colours with contrasting colour combinations. As in this case we are testing with a screen reader, this is of no importance to our test scenario.
The Always use Page Layout Style setting allows us to override the page layout style option. Here we have chosen the Single Page Continuous option. Otherwise, a search would only reveal the results of a single page. We do not touch the Zoom Setting as we want to keep it as intended by the creator of the document.
We always want to activate the option Use document structure for tab order when no explicit tab order is specified, which improves the navigation of form fields and links in documents that do not specify a tab order. Of course, we always want the option Enable assistive technology support to be activated, which allows the NVDA screen reader to access the document.
We do not change any of the other options as they address users with screen magnifiers and colour deficiencies. The Reading panel offers an option to specify the reading order of documents. The recommended option is Infer reading order from document. A screen reader will interpret the reading order of untagged documents by using advanced layout analysis. Please note that your documents should always be tagged to offer the best reading experience to users with visual impairments.
There are more options for fine-tuning the reading experience for users with disabilities. For a more extensive explanation, please refer to the Adobe documentation.
The demo
Before starting our demo, we made sure that our document passed all the tests we described in the Testing PDFs chapter.
We are therefore sure that the PDF is error-free and that the basic accessibility features are working. We are using document tagging, semantic elements and alternative texts.
We have prepared a simple document. For our demo, we open the document using Acrobat Reader, but we could also use Acrobat Pro.
The Wonderland Gazette is an imaginary newspaper in the world of Alices Adventures in Wonderland. At the top of the page, we can see the main heading of our newspaper. Below, we see a set of four articles, each with a heading of its own. At the bottom of the page is an advertising block.
We start the NVDA screen reader.
[Screen reader:] 1/1 C Users…
[Narrator:] By pressing the Control key we can stop the speech output.
Acrobat Reader offers a set of function blocks. To navigate between the various function blocks we use the F6 key.
[Screen reader:] Find Tools button. Home button. Tool bar. Start this file button. Document 1/1 C Users…
[Narrator:] As we are not used to speech output, we turn it off and will use the output of the Speech Viewer only. To switch the speech output off, press Insert + S.
[Screen reader:] Speech mode off.
[Narrator:] Please note that whenever we mention the Insert key, we are referring to the NVDA modifier key.
Let’s take our first steps in the document. We will use the Down arrow key to go through the document element by element. We can go back again by pressing the Up arrow.
As this approach only offers us a sequential way of reading the document elements, we prefer to use the structure of the document to speed up our navigation experience. To navigate from heading to heading we can press H. You can see how we navigate from heading to heading using the Speech Viewer and the Visual Highlight. We can reverse the navigation direction using Shift + H.
We can use the G key to navigate from graphic to graphic. And, of course, we can use Shift + G to reverse the direction. In the next set of examples we won’t mention again that the Shift key can be used to reverse the navigation direction, but it can be used in all of them. In the same way, we can use the L key to search for lists, the T key for tables, and the K key for links. And the F key takes us to form fields.
To get an overview of links and headings we can open the Elements List by pressing Insert + F7. Using Shift + Tab we can move the cursor to the element type selection. To select the element type, press the Right and Left arrow keys. To get back to the element list, press the Tab key. We can navigate to the selected element by pressing Enter. We can leave the dialogue box using the Escape key.
Let’s try to navigate inside a text. We press 9 or 7 on the numeric keypad for the next or previous line, 6 or 4 for the next or previous word, and 3 or 1 for the next or previous character.
Here we see a text block that uses multiple languages. Using the silent mode, we do not notice any difference in the presentation. We therefore switch the Speech mode on and continue reading.
[Screen reader:] Speech mode beeps.
[Narrator:] When we switch, NVDA first activates the Speech mode beeps, which activates a beep between each navigation step.
[Screen reader:] Speech mode talk.
[Narrator:] When we switch again, we activate Speech mode talk.
[Screen reader:] … many languages and is read by people… List with 4 items. Bullet. France. [In French] Aventures d’Alice au pays des merveilles. Bullet. Germany. [In German] Alice’s Abenteuer im Wunderland. Bullet. Italy. [In Italian] Le Avventure d’Alice nel Paese delle Meraviglie. Bullet. Spain. [In Spanish] Alicia en el País de las Maravillas. Out of list. This has come as a surprise to many of us.
[Narrator:] This is how it is supposed to work.
Potential error scenarios
When we prepared this document, we incorporated various problems that are difficult to find without using a screen reader. We will not explain how to fix them as that was part of the chapters From Word to PDF, Adobe InDesign and Repairing PDFs with Adobe Acrobat.
When we start navigating the document we notice that the content is not read in the sequence as it appears visually. The visual sequence should always match the sequence in which a screen reader reads the elements. Their sequence obviously needs to be corrected.
Have you noticed that the image descriptions of two images have accidentally been exchanged? We need to switch them to correct this. Bugs like these are difficult to find when the alternative text stays hidden from a sighted user.
When we navigated using the headings, one of them was missing. This heading was obviously not tagged as a heading; it is just visually presented in the same way as one.
The same is true for the list. The list was not marked as a list using the tagging, so the screen reader cannot find it.
[Screen reader:] Speech mode beeps. Speech mode talk. Speech mode beeps. Speech mode talk. … many languages and is read by people all over the world, as in: List with 4 items. Bullet. France. [Read in English] Aventures d’Alice au pays des merveilles. Bullet. Germany. [Read in English] Alice’s Abenteuer im Wunderland. Bullet. Italy. [Read in English] Le Avventure d’Alice nel Paese delle Meraviglie. Bullet. Spain. [Read in English] Alicia en el País de las Maravillas. This has come as a surprise to many of us, who have always thought of Wonderland as our secret home.
[Narrator:] In this implementation the texts are not read out using the correct language. The elements do not contain any attributes that would help a screen reader find a matching voice. When using a screen reader, it is easy to come across texts that are read out using a voice that does not match the language in which they are written.
[Screen reader:] Speech mode off.
[Narrator:] The advertising block is not part of the tagging; therefore the screen reader cannot find it. This was not intentional. We want a visually impaired user to be able to access all content. As you have seen, there are accessibility problems that cannot easily be detected without a screen reader.
Keyboard shortcuts
Here is a summary of the keyboard combinations we have used during this tutorial.
Please note that you can download a quick reference guide with a summary of all of the key commands we use.
Where to continue?
You have now had an introduction to testing PDF documents with NVDA.
Depending on your interests, you could continue with the following chapter:
- Testing publications with NVDA: EPUBs.
[Automated voice:] Accessibility. For more information visit: op.europa.eu/en/web/accessibility.