PDF/UA-1: Pages with link annotations missing tab order (S entry)

[bryskhe]

Description

When a Typst document contains link annotations (e.g. #link, TOC entries, cross-references), the PDF pages that contain these links do not have their tab order (S entry in the page dictionary) set to S (document structure). This violates PDF/UA-1 Matterhorn checkpoint G4_F07 ("Tab order for pages with annotations missing").
The result is that PDF accessibility checkers (e.g. Adobe Acrobat) report incorrect or undefined tab order on pages with links, and keyboard users may experience non-logical tab navigation.
To reproduce: Create a document with #outline() and any #link() or cross-reference. Export with --pdf-standard ua-1. Open in Acrobat and run the full accessibility check.
Expected: All pages with annotations should have tab order set to follow document structure.
Typst version: 0.14.2

Operating system

Windows

Typst version

• I am using the latest version of Typst

[LaurenzV]

That's weird, in theory it should always be set...

https://github.com/LaurenzV/krilla/blob/88483e26b6c56d55463910ee4e300ab149df9c36/crates/krilla/src/page.rs#L433-L440

[LaurenzV]

#set document(title: "The document title")
#outline()
#set heading(numbering: "1)")

= Hi there <a>

In @a, you can see this.

Does this trigger it for you? At least in veraPDF this seems to pass fine, unfortunately I don't have an Acrobat subscription anymore so I can't test it there. :(

[bryskhe]

Thank you for the quick response — really appreciated! Good news on the tab order: no complaints from Acrobat Pro on the minimal example. So that part seems to be working correctly. 🎉 I should mention that I don't have Acrobat myself, so I'm relying on a colleague who has Acrobat Pro (Continuous Release 2024.005.20399, 64-bit) to do the testing for me. She did find one issue though — the minimal example fails on Lists > Lbl/LBody. The error appears as Lbl/LBody 1 under the Lists check. She found the description of the error here<https://helpx.adobe.com/acrobat/using/create-verify-pdf-accessibility.html#LblLBody> — though we're not entirely sure what's causing it in this case. Our best guess is that it's related to #set heading(numbering: "1)") generating a label that isn't wrapped in the correct PDF tag structure, but we could be wrong. Happy to test further if you can suggest a smaller example that isolates the issue, or if you have a specific fix you'd like us to try! Från: Laurenz Stampfl ***@***.***> Skickat: den 16 mars 2026 17:56 Till: typst/typst ***@***.***> Kopia: Bryskhe Henrik ***@***.***>; Author ***@***.***> Ämne: [EXTERNT] Re: [typst/typst] PDF/UA-1: Pages with link annotations missing tab order (S entry) (Issue #7990) OBS! Detta mejl kommer från en avsändare utanför vår IT-miljö. Klicka inte på länkar och öppna inte bifogade filer om du är osäker på avsändare eller innehåll. Kontakta Service Desk om du behöver råd och stöd. [https://avatars.githubusercontent.com/u/47084093?s=20&v=4]LaurenzV left a comment (typst/typst#7990)<#7990 (comment)> #set document(title: "The document title") #outline() #set heading(numbering: "1)") = Hi there <a> In @A, you can see this. Does this trigger it for you? At least in veraPDF this seems to pass fine, unfortunately I don't have an Acrobat subscription anymore so I can't test it there. :( — Reply to this email directly, view it on GitHub<#7990 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/BQ6SMCN2BTXAOKRP6EA7TWT4RAW3JAVCNFSM6AAAAACWTMPRQSVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DANRZGE2TQNJZGY>. You are receiving this because you authored the thread.Message ID: ***@***.******@***.***>>

[saecki]

She did find one issue though — the minimal example fails on Lists > Lbl/LBody. The error appears as Lbl/LBody 1 under the Lists check. She found the description of the error herehttps://helpx.adobe.com/acrobat/using/create-verify-pdf-accessibility.html#LblLBody — though we're not entirely sure what's causing it in this case. Our best guess is that it's related to #set heading(numbering: "1)") generating a label that isn't wrapped in the correct PDF tag structure, but we could be wrong.

Adobe uses a non standard compliant check for the use of Lbl tags, so this is expected, but seems unrelated to the original issue.

Since we can't reproduce the issue, it would be very helpful if you could provide an ideally minimal Typst example document that triggers the check.

[bryskhe]

Hi again, and thanks for staying on this with us — really appreciated! 😊 We've done more testing and have some new findings to share. First, a correction from our previous message — we now believe the Lbl/LBody issue and the tab order issue are two separate bugs. We'll focus on the tab order here. We've been systematically narrowing down what triggers the tab order error in Acrobat, and we've arrived at something surprisingly minimal. Even this document triggers it: #set document(title: "Tab order test") #set page(paper: "a4") Page 1 #pagebreak() Page 2 No headers, no footers, no links, no headings — just two pages of plain text. Compiled with --pdf-standard ua-1. Looking at the code Laurenz linked earlier, we noticed that the tab order S entry is currently only written when !self.annotations.is_empty(). Our guess is that Acrobat requires the tab order entry to be set on all pages, not just pages that have annotations. Could that be the issue? We're testing via a colleague with Acrobat Pro (Continuous Release 2024.005.20399, 64-bit) since we don't have Acrobat ourselves. Happy to keep testing if you have more things you'd like us to try! Från: Tobias Schmitz ***@***.***> Skickat: den 17 mars 2026 10:49 Till: typst/typst ***@***.***> Kopia: Bryskhe Henrik ***@***.***>; Author ***@***.***> Ämne: [EXTERNT] Re: [typst/typst] PDF/UA-1: Pages with link annotations missing tab order (S entry) (Issue #7990) OBS! Detta mejl kommer från en avsändare utanför vår IT-miljö. Klicka inte på länkar och öppna inte bifogade filer om du är osäker på avsändare eller innehåll. Kontakta Service Desk om du behöver råd och stöd. [https://avatars.githubusercontent.com/u/43008152?s=20&v=4]saecki left a comment (typst/typst#7990)<#7990 (comment)> She did find one issue though — the minimal example fails on Lists > Lbl/LBody. The error appears as Lbl/LBody 1 under the Lists check. She found the description of the error herehttps://helpx.adobe.com/acrobat/using/create-verify-pdf-accessibility.html#LblLBody — though we're not entirely sure what's causing it in this case. Our best guess is that it's related to #set heading(numbering: "1)") generating a label that isn't wrapped in the correct PDF tag structure, but we could be wrong. Adobe uses a non standard compliant check for the use of Lbl tags, so this is expected, but seems unrelated to the original issue. Since we can't reproduce the issue, it would be very helpful if you could provide an ideally minimal Typst example document that triggers the check. — Reply to this email directly, view it on GitHub<#7990 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/BQ6SMCMWXMVLC4IRG6HU6GT4RENRDAVCNFSM6AAAAACWTMPRQSVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DANZTGY2TENBXGQ>. You are receiving this because you authored the thread.Message ID: ***@***.******@***.***>>

[saecki]

Thanks for the minimal reproduction example.

Our guess is that Acrobat requires the tab order entry to be set on all pages, not just pages that have annotations. Could that be the issue?

Yes, that seems to be the issue. Since The PDF/UA-1 specification (7.18.3 Tab order) explicitly states that this is only required when there are annotations on the page, I think this is an issue with Acrobat, not Typst/krilla:

Every page on which there is an annotation shall contain
in its page dictionary the key Tabs ...

We try to adhere to the official PDF specifcations, and Adobe Acrobat implements some checks that are either not mentioned in the spec, and sometimes even contradict it. The one discussed here just seems like a bug to me. We suggest using other tools like PAC or veraPDF to validate accessibility of PDF files. Here is a list from the PDF association: https://pdfa.org/tools-for-accessible-pdf/

[LaurenzV]

I mean, I would be fine changing the behaviour if it helps, it's not a big deal just always adding it, after all. Or is there something speaking against this?

[saecki]

I guess not, maybe I was a bit quick to close this, since the behavior is technically correct. But one extra entry per page isn't really an issue.

[bryskhe]

That sounds perfect to us! We can't think of anything speaking against it - always setting it seems like the safer and more correct behavior regardless. Thank you for being so responsive and willing to fix this! Från: Laurenz Stampfl ***@***.***> Skickat: den 17 mars 2026 15:33 Till: typst/typst ***@***.***> Kopia: Bryskhe Henrik ***@***.***>; Author ***@***.***> Ämne: [EXTERNT] Re: [typst/typst] PDF/UA-1: Pages with link annotations missing tab order (S entry) (Issue #7990) OBS! Detta mejl kommer från en avsändare utanför vår IT-miljö. Klicka inte på länkar och öppna inte bifogade filer om du är osäker på avsändare eller innehåll. Kontakta Service Desk om du behöver råd och stöd. [https://avatars.githubusercontent.com/u/47084093?s=20&v=4]LaurenzV left a comment (typst/typst#7990)<#7990 (comment)> I mean, I would be fine changing the behaviour if it helps, it's not a big deal just always adding it, after all. Or is there something speaking against this? - Reply to this email directly, view it on GitHub<#7990 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/BQ6SMCLPCNKYUGFLKRFCOOL4RFOX7AVCNFSM6AAAAACWTMPRQSVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DANZVGQZDIOBTGM>. You are receiving this because you authored the thread.Message ID: ***@***.******@***.***>>