Tags are one of the most important aspects of accessible PDF files. An untagged PDF can be read by assistive technology, however the user agent is really just guessing at what the author intended and the screen reader will be reading the guesses. A screen reader reads the tag structure and therefore the tags must be in order and the content must be properly tagged for a PDF file to be truly accessible.
If you’re familiar with HTML, you’ll notice that tags in a PDF are very similar to HTML tags. You’ll recognize many of the same tags, such as <P> for paragraph, <TR>, <TD> and, <TH> for table row, table data cell and table header cell, respectively. You’ll also recognize list and list item tags: <L> and <LI>
Some differences between PDF and HTML tags are:
- PDF tags are case-sensitive whereas HTML tags are not
- It seems that you can create your own PDF tag, whereas HTML tags are pre-defined. PDF tags seem to work more like XML tags in that way (but make sure you’ve mapped the new tag to an existing tag by editing the roll map — see below for directions)
Right click on the new tag and select Edit Role Map
If the tag is not mapped (doesn’t show up in the Role Map window), select New Item
Then type the name of your new tag in the top form field of the Add Role window that opens and use the drop-down menu to find the role to which you want to map your new tag. Click OK
Your new tag will show up in the Role Map window as being mapped to the role you just chose.