Why is all this stuff below about tags! Well... screen readers only read the tags in a PDF. If none are added, nothing is read. If the tags are not structured correctly, then it does not read correctly or even make sense in many cases. PDF tags resemble HTML tags roughly and you can imagine if that HTML tags were all out of order, a web page would be a mess, the same can happen with the screen reader user. Conversions from MS Word and other documents to a PDF with automatic tags  are never completely accurate, and they need our help to make it read the way the author intended.

Figure 4: Fully expanded different types of tags.

Here are different types of tags.  As noted some tags have their own special icon that makes them easier to stand out. These are not fully expanded as indicated by the plus icon [+] (common in applications to mean the item can be expanded, [-] is full expanded and can be unexpanded if CLICKed). 

Figure 2: Tag container icon - holds text.

Figure 1: Basic tag icon.

2. The Wonderful World of Tags

2.1. What To Do?

The tags are the most important to work on, so we address that first. Then we tackle descriptions for images, and finally overall structure. A tag is represented by an icon that is a luggage tag. A tag holds a container which has a shoebox as an icon. The container holds the content. Tag -> Container -> Content. Some tags have sub-tags such as bullet or number lists and links. Figure tags hold the reference to the image.

Visually let’s take a quick look before we understand them a bit more:

Here is the basic tag.

Here are those same tags - from Figure 3 -  fully expanded. Each shows what they contain. Both tables and lists have sub-tags to format and control how the content is structured. Various types of links also have sub-tags though not in all cases. A Table of Contents with links is more complicated than a simple web link.

Figure 3: Types of tags and their icon.

The basic tags we need to know for our effort here are:

<P> for unformatted or plain text called Paragraph text by Acrobat
<Table> the start tag (tree with branches), <TR> Table Row, <TD> Table Data, <TH> Table Header
<L> start tag number or bullet list, <LI> List Item
<Link> just like it says
<Figure> as in an image