This is the second in a series of posts to help you make your PDF files accessible. In the last post we described some of the document properties necessary for overall accessibility. Now we go on to resolving issues within the document content.
To repair content issues the file must first be tagged. If your file is already tagged, you can miss this step and read on from the Working with the Touch Up Reading Order tool heading.
Auto tagging
To save you a good deal of time, Adobe Acrobat Pro can start the tagging process. It makes a reasonable job of identifying tables and lists, but is limited in it's recognition of heading structure and can't describe your images for you. However it will define tags for most content, and you can edit these as necessary.
Follow the menu path: Advanced > Accessibility > Add tags to document
When the auto tagging is complete, a report is produced in the left frame, giving links to potential issues and hints for repair. You can work through this list now, or do it later, after other remedial work.
However, before you begin working through the accessibility report list, do two things.
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Save this copy as a different version from the last one.
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Visually compare this version with the original. If there are unacceptable visual differences you may need to revert to your previous version and tag all or part of the file manually.
Working with the Touch Up Reading Order tool
Most of the tagging repair and correction will be done in the Touch Up Reading Order tool. Open it now:
Follow the menu path: Advanced > Accessibility > Touch Up Reading Order
A dialog will appear with a wide array of options, just select the button "Show Order panel".
A group of panels will then appear, containing the Content, Order and Tags panels.
In the background you will find that the document has had some temporary additions made. This is the overall reading order and consists of numbered boxes. The numbers represent the order (and match the content in the Order panel). The borders show the parameters of each block.
We'll be working in the Order and Tags panels to repair or correct any reading order issues, but before discussing how, let's look at what issues to look for.
Logical reading order
The actual reading order of text in a PDF file can be very different from the visual reading order, though most conversions from well structured Word documents will have no problems.
Reading order problems can arise from a range of design decisions, especially in files that need to be made accessible after creation, these include:
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Column layout that is improperly structured and forces text to be read across each column, line by line, rather than in column order.
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Background images "grouping" two or more pieces of semantically unrelated text, taking them out of their logical order and joining them as a single block.
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Words that have spaces inserted between each letter for visual effect, for instance, E d I t o r' s N o t e. This would force a screen reader to spell the words, rather than to read them.
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Narrow gutters between columns can make two or three column text blocks join in the background, so that the actual reading order is line by line, across all columns.
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An unknown cause of a frequently encountered problem with multi-column text is where there doesn't appear to be an actual space between the last word of one line and the first word of the next, so that although they are visually separated by line breaks, the actual text has the last word of each line joined to the first word of the next line as single words.
Any of the above will make reading a document difficult or impossible through a speech or Braille output screen reader.
Reading order requirements:
The actual reading order of text needs to be logical, or an ALT text can be provided to "cover" any text that can't have its order physically changed. Note though that ALT attributes can't be used in table cells. They just render the cell content invisible to some screen readers.
To check for reading order issues
You can check the reading order by either saving the PDF as a text document and inspecting this for reading order problems or by running a screen reader over the document, listening for any of the issues mentioned above.
Correcting reading order issues
Working in the Order panel
The Order panel shows content as numbered items within each page of the document.
The tasks you can perform here include defining the content type and changing the composition or order of blocks of text.
Navigate the document looking for any text that is obviously not in the correct order, or not in the order at all.
Adding text to the order
If you find text that isn't surrounded by a box, then it isn't in the reading order.
Draw a rectangle with your mouse on the document, then right click to add it to the order. The right click gives you access to a wide range of tags. If the one you want isn't there, just choose "tag as text", it can be corrected later in the Tags panel.
Always double check in the Order panel list to ensure that nothing has jumped out of order when you have added new content to the order.
Changing order
To check that text is in the correct order, look at the file view and check that each block surrounding text has a number that represents the logical order. For instance, if the block at the top of the page has the reference number "3", and the one below it is numbered "1", this is unlikely to be a logical order.
Change order by putting the focus on the corresponding number in the Order panel, (the page view number gets a blue background). Now drag the Order entry up or down the list to put it in the correct order.
Background images
A number of the images, or Figures, as they are tagged, will not convey information. You should make them "disappear" from screen reader view. This won't or shouldn't affect the way they look on the page.
Save to a new version before this, it may make visible changes.
To turn a Figure into a background image, in the Order panel, put the focus on the entry with the same order number as the image, right click and select "Tag as background".
The above will sort out any larger reading order issues, now for a little fine tuning, we need to use the Tags panel.
Working in the Tags panel
The Tags panel shows content as individual tags often within container tags like <partetc. It's document wide, not page by page. Container tags are normally defined by the authoring tool.
The tasks you can perform here include changing tag values, amending heading levels, adding ALT text to images or text with reading order problems, repairing lists and defining header cells in tables. It's the fine tuning panel.
To make most changes you'll right click any tag, choose An option, usually Properties, and make changes.
Fine tuning reading order issues
Check the text document version of your PDF, if any text is malformed then:
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Identify the containing tag, (selecting the "Highlight content" option will help here.;
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Find and repair it in the text version;
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Then copy the repaired text;
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Back to the PDF, right click the container in the Tags tree, select Properties, and paste the repaired text into the "Alternative text" box.
Now take a text copy of your repaired reading order PDF, and make sure that all text makes sence.
That's all for now, next we'll check and repair any structural issues.