Over time I have seen a variety of ways to create Reference and Note tags. It can be tedious using assistive technology to locate referenced content. There are rules for applying Reference and Note tags, and there is a future thought process by governing bodies.
Should you wish to look up the specifications, please see PDF/UA ISO_14289-1;2012 – 7.9 Notes and references, and, PDF v1.7 specification (ISO PDF 32000-1:2008, Table 338).
How it works
PDF internal document links do not link to specific content. You can only link to the page level. If a link happens to bring an end user to the exact content, it is likely because that content happens to be at the top of the page.
If there are multiple References on a page to the same Note, place each note into a Note tag and place them at the end of the page in the logical reading order. If there is one Reference on a page to a footnote, using the logical reading order, the Note may be placed directly after the Reference tag. The end user shouldn’t have to remember where the Reference was so they can go back to that point to re-read the Note.
The superscript character that references information within the document must be placed in a <Reference> tag. Actual or alternate text may only be applied if the character is not read properly by the assistive technology.
Footnotes or endnotes must be placed in a <Note> tag. The reference character is placed in a label <Lbl> and the body of the note is placed in a <P> tag.
Each Note must have a unique ID.
A Reference tag will appear in the screen reader link list although it does not contain link capabilities. While you can insert a document link, remember that it will only take the user to the top of that page or zoomed view. The end user will have access to the referenced character. You may apply expansion text or alternate text to identify where the note is within the document.
Unfortunately, there are no screen reader keyboard commands to bring you directly to a Note tag yet. In the future, the purpose of the Note ID will be to associate the Reference tag to the Note tag. This capability is not available yet.
By following the rules and the techniques above you will provide end users a consistent way to locate and access referenced materials.