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From: Alan O'Flanagan
Date: Thu, Apr 10 2025 2:27AM
Subject: Reference/Note tags
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Hi Every,
I'm new to accessibility and currently working on making PDFs UA-compliant. While I've managed to resolve most issues, I've now encountered a situation where the information seems to contradict itself. Specifically, I'm trying to create an internal "Reference" tag and a corresponding "Note" tag.
I attempted the following structure, but the software I'm using indicates that the <Lbl> tag should not be nested within a <Reference> tag:
<Reference> {
<Lbl> {1)}
}
<Note> {
<Lbl> {1)}
<P> {The first idea is to understand footnotes}
}
For reference, I've been consulting documentation from ISO-TS-32005-2023.pdf, ISO-14289-2-2024.pdf, and the Tagged PDF Best Practices Guide from the PDF Association. From what I understand, the reading order should place the note immediately after the reference.
Any insight you could provide would be greatly appreciated.
Best regards,
Alan

From: Laura Roberts
Date: Thu, Apr 10 2025 7:59AM
Subject: Re: Reference/Note tags
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I've never used a Lbl tag within a reference tag.

The structure is:
<Reference>
<Link>
Text
Link objr

Best regards,
Laura Roberts
413-588-8422

On Thu, Apr 10, 2025, 4:27 AM Alan O'Flanagan via WebAIM-Forum <
= EMAIL ADDRESS REMOVED = > wrote:

> Hi Every,
> I'm new to accessibility and currently working on making PDFs
> UA-compliant. While I've managed to resolve most issues, I've now
> encountered a situation where the information seems to contradict itself.
> Specifically, I'm trying to create an internal "Reference" tag and a
> corresponding "Note" tag.
> I attempted the following structure, but the software I'm using indicates
> that the <Lbl> tag should not be nested within a <Reference> tag:
> <Reference> {
> <Lbl> {1)}
> }
> <Note> {
> <Lbl> {1)}
> <P> {The first idea is to understand footnotes}
> }
> For reference, I've been consulting documentation from
> ISO-TS-32005-2023.pdf, ISO-14289-2-2024.pdf, and the Tagged PDF Best
> Practices Guide from the PDF Association. From what I understand, the
> reading order should place the note immediately after the reference.
> Any insight you could provide would be greatly appreciated.
> Best regards,
> Alan
>
>
>

From: Paul Rayius
Date: Thu, Apr 10 2025 8:08AM
Subject: Re: Reference/Note tags
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Hi Alan,
Regarding your documentation that you're using - and probably your validation tool:
ISO-TS-32005-2023, and ISO-14289-2-2024 are for PDFs in the PDF 2.0 context, using ISO 32000-2. Meanwhile, the current "Tagged PDF Best Practices Guide," from the PDF Association is based on PDF/UA-1 (and, therefore, ISO 32000-1). Also, "most" PDF validators out there now, currently in use, are validating against PDF/UA-1. So, while it might be allowed, and appropriate, in the PDF 2.0 / PDF/UA-2 context, to have a Lbl inside a Reference, that's not allowed in PDF/UA-1.

I hope that helps,
Paul

Paul Rayius, ADS
VP, Customer Support and Training
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From: Philip Kiff
Date: Thu, Apr 10 2025 12:57PM
Subject: Re: Reference/Note tags
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Following up on the use of Lbl (Label) tags in PDF/UA-1. I guess I'm not
sure where in the various standards it says that we can't have an Lbl
tag nested inside a Reference tag?

I always find the Lbl tags confusing because there are significant
shifts between different versions. Even within PDF/UA-1, there is a bit
of contradiction with them being included in the BLSE (Block-Level
Structure Elements) table, when they are clearly being treated as ILSE
(Inline-Level Structure Elements) elsewhere.

I think someone may have previously pointed out to me where this rule
exists in PDF/UA-1, but I can't seem to find it now.

Thanks,

Phil.

On 2025-04-10 10:08 a.m., Paul Rayius via WebAIM-Forum wrote:
> [....] So, while it might be allowed, and appropriate, in the PDF 2.0 / PDF/UA-2 context, to have a Lbl inside a Reference, that's not allowed in PDF/UA-1.

From: Philip Kiff
Date: Mon, Apr 14 2025 11:18AM
Subject: Re: Reference/Note tags
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I didn't see a reply to my response about <Lbl> tags with <Reference>
and <Note> tags last week. But the question of how best to tag
References is an issue that I notice keeps cropping up in different
contexts and forums from time to time, so I thought I'd summarize my own
current take on it all.

First, to put this in context, the question of how to use <Lbl> is
really a technical standards question that does not currently affect
practical accessibility for ANY user agents reading PDF files. As far as
I know, screen readers, Braille displays, and other assistive
technologies don't treat <Lbl> tags any differently than either <Span>
or <P> tags, and PDF software doesn't actually connect any number or
character inside an <Lbl> tag with a corresponding <Reference> or <Note>.

For that matter, <Reference> and <Note> tags don't really make much
difference to anyone either. Though <Reference> is sometimes read
(incorrectly) as "Link" in some screen readers. This will all change
when PDF 2.0 becomes more widely adopted, but currently, folks are still
targeting PDF 1.7 and PDF/UA-1.

So at the moment, actual people reading PDFs will not be affected by
whatever structure you choose to use for <Lbl> tags. Whew!

Having said that, I personally think that the "best practice" is to
follow the latest version of the Tagged PDF Best Practices Guide from
the PDF Association. This is what the original poster, Alan, suggested
in the first post in this thread.

I have a few additional recommendations for folks aiming to achieve best
practices, but these are my own personal suggestions and are not
supported by any specific standard or guideline. I like to always add a
link to footnote/endnote reference numbers and a backlink from the note
to the reference number in the body text so that visual readers can jump
back and forth to the footnote and its reference easily. I also
recommend enclosing footnote/endnote reference number in square brackets
to increase the target size of that link and to generally make it easier
for readers to notice that there is a note number there. And I customize
the font size of footnote numbers so that they are not so small as to be
difficult to read - default note styles using superscript in both Word
and InDesign shrink the notes too much and often make it hard for
everyone to read.

Putting all this together, you end up with a tag structure something
like (bullets representing nested levels):

<Reference>
• <Link>
• • Link-OBJR
• • [
• • <Lbl>
• • • 1
• • ]
<Note>
• [
• <Lbl>
• • 1
• [
• <P> or <Span> depending on the content of the Note.

However, as Alan noted, some PDF checking software that will flag one or
both uses of <Lbl> above as an error.

Adobe Acrobat's built-in checker flags any <Lbl> that isn't nested
inside an <L> as an error by default. You can turn off this check in
Acrobat's settings by clearing the "Lbl and LBody must be children of
LI" checkbox.

CommonLook PDF I think flags the <Lbl> nested in the <Reference> tag as
an error, but passes the <Lbl> nested inside the <Note> tag. I think
that's probably based on what I view as an overly restrictive reading of
Table 338 - Standard structure types for inline-level structure elements
on page 588 of PDF 32000-1, which is referred to in the PDF/UA-1
standard. The Description for the <Note> tag in Table 338 explicitly
says that "it may have a label", whereas the description for the
<Reference> tag does not mention labels. A more permissive reading like
mine allows for a Reference tag also to include a nested <Lbl> tag.

There is a bit more nuance to the question of what the standards
actually say because we now know that <Lbl> was incorrectly included in
Table 334 - Block-level structure elements on page 585. And we also know
that in the new versions of the PDF standards (PDF 2.0 and ISO 32000-2),
<Lbl> is now always considered an inline-level structure - or a special
List type. And a new RefNote tag is introduced in PDF 2.0. Though if one
wants to future-proof a PDF, using only <Reference> and <Note>, then I
think including the <Lbl> as the glue in both is still advisable.

If you want to pass all the checkers, and not have to explain to a
client or boss why your PDF fails some checks despite following what you
may consider to be best practices, then I would recommend following
Laura Robert's very concise and helpful suggestion earlier in this
thread to simply not include an <Lbl> tag within a reference tag and use
the following structure for the Reference:
<Reference>
• <Link>
• • 1
• • Link objr

I'd still recommend surrounding the note number in square brackets, but
that won't affect whether you pass a validator.

I'd welcome any corrections or alternate views on any of this!

Phil.

Philip Kiff
D4K Communications

On 2025-04-10 2:57 p.m., Philip Kiff via WebAIM-Forum wrote:
> Following up on the use of Lbl (Label) tags in PDF/UA-1. I guess I'm
> not sure where in the various standards it says that we can't have an
> Lbl tag nested inside a Reference tag?
> [....]
>
> On 2025-04-10 10:08 a.m., Paul Rayius via WebAIM-Forum wrote:
>> [....] So, while it might be allowed, and appropriate, in the PDF 2.0
>> / PDF/UA-2 context, to have a Lbl inside a Reference, that's not
>> allowed in PDF/UA-1.

From: Duff Johnson
Date: Tue, Apr 15 2025 1:06PM
Subject: Re: Reference/Note tags
← Previous message | No next message

> I didn't see a reply to my response about <Lbl> tags with <Reference> and <Note> tags last week. But the question of how best to tag References is an issue that I notice keeps cropping up in different contexts and forums from time to time, so I thought I'd summarize my own current take on it all.
>
> First, to put this in context, the question of how to use <Lbl> is really a technical standards question that does not currently affect practical accessibility for ANY user agents reading PDF files.

In lists, <LbL> elements distinguish the list item’s label from the <LBody> (the content of the LI). <Lbl> was more broadly (but poorly) defined in PDF 1.x. This situation was addressed in PDF 2.0, but implementations are only now beginning to arrive.

> As far as I know, screen readers, Braille displays, and other assistive technologies don't treat <Lbl> tags any differently than either <Span> or <P> tags,

…when not in the context of a list. We can only hope (and push!) for better implementations.

> and PDF software doesn't actually connect any number or character inside an <Lbl> tag with a corresponding <Reference> or <Note>.

"PDF software" can do whatever it likes, including assisting with the PDF Association’s Best Practice guidance on this point, as you’ve noted… but, yes, the PDF specification doesn’t include special structures for this purpose.

> For that matter, <Reference> and <Note> tags don't really make much difference to anyone either.

Same problem.

> Though <Reference> is sometimes read (incorrectly) as "Link" in some screen readers.

This is a confusing aspect of the old spec, which is why it gets a lot of attention in the Best Practice Guide.

> This will all change when PDF 2.0 becomes more widely adopted, but currently, folks are still targeting PDF 1.7 and PDF/UA-1.

True, and thus, it’s confusing today. :-(

> So at the moment, actual people reading PDFs will not be affected by whatever structure you choose to use for <Lbl> tags. Whew!

Unlike web pages, PDF files persist. Unlike the experience of a browser session, people actually take possession of PDF files, and expect them to work into the (potentially) distant future.

Web pages can be fixed for everyone by a tweak and a reload. By contrast, PDF is often "delivered" rather than "served", so if it’s inaccessible on-delivery it’s generally inaccessible for every downstream user, forever.

That’s why PDF accessibility isn’t - and should never be - just about today’s software.

Ok, I’m a romantic. :-)

> Having said that, I personally think that the "best practice" is to follow the latest version of the Tagged PDF Best Practices Guide from the PDF Association. This is what the original poster, Alan, suggested in the first post in this thread.

+1 :-D

> I have a few additional recommendations for folks aiming to achieve best practices, but these are my own personal suggestions and are not supported by any specific standard or guideline. I like to always add a link to footnote/endnote reference numbers and a backlink from the note to the reference number in the body text so that visual readers can jump back and forth to the footnote and its reference easily.

Software should be able to use the existing structures to do this without links, but in the absence of such I applaud such attention to detail!

> I also recommend enclosing footnote/endnote reference number in square brackets to increase the target size of that link and to generally make it easier for readers to notice that there is a note number there. And I customize the font size of footnote numbers so that they are not so small as to be difficult to read - default note styles using superscript in both Word and InDesign shrink the notes too much and often make it hard for everyone to read.

Nice! Authors, take note!

> Putting all this together, you end up with a tag structure something like (bullets representing nested levels):
>
> <Reference>
> • <Link>
> • • Link-OBJR
> • • [
> • • <Lbl>
> • • • 1
> • • ]
> <Note>
> • [
> • <Lbl>
> • • 1
> • [
> • <P> or <Span> depending on the content of the Note.

+1

> However, as Alan noted, some PDF checking software that will flag one or both uses of <Lbl> above as an error.
>
> Adobe Acrobat's built-in checker flags any <Lbl> that isn't nested inside an <L> as an error by default. You can turn off this check in Acrobat's settings by clearing the "Lbl and LBody must be children of LI" checkbox.
>
> CommonLook PDF I think flags the <Lbl> nested in the <Reference> tag as an error, but passes the <Lbl> nested inside the <Note> tag. I think that's probably based on what I view as an overly restrictive reading of Table 338 - Standard structure types for inline-level structure elements on page 588 of PDF 32000-1, which is referred to in the PDF/UA-1 standard. The Description for the <Note> tag in Table 338 explicitly says that "it may have a label", whereas the description for the <Reference> tag does not mention labels. A more permissive reading like mine allows for a Reference tag also to include a nested <Lbl> tag.

I encourage you to share your observations with the vendors concerned. I know they listen to their users.

> There is a bit more nuance to the question of what the standards actually say because we now know that <Lbl> was incorrectly included in Table 334 - Block-level structure elements on page 585.

Table 334 in PDF 1.7 is… unfortunate.

There’s a reason why the definition of Tagged PDF was overhauled between PDF 1.7 and PDF 2.0!

> And we also know that in the new versions of the PDF standards (PDF 2.0 and ISO 32000-2), <Lbl> is now always considered an inline-level structure - or a special List type. And a new RefNote tag is introduced in PDF 2.0. Though if one wants to future-proof a PDF, using only <Reference> and <Note>, then I think including the <Lbl> as the glue in both is still advisable.
>
> If you want to pass all the checkers, and not have to explain to a client or boss why your PDF fails some checks despite following what you may consider to be best practices, then I would recommend following Laura Robert's very concise and helpful suggestion earlier in this thread to simply not include an <Lbl> tag within a reference tag and use the following structure for the Reference:
> <Reference>
> • <Link>
> • • 1
> • • Link objr

I get it. The lowest-common-denominator usually "wins" while AT users - who, without label tags, are left by themselves to distinguish label from content - are the losers. :-(

We can only hope that, over time, assets such as the PDF Association's Techniques for Accessible PDF will help to elevate common understanding.

Duff.