Conference 17–18 May 2021 📍 Online

PDF Days Europe 2021 — First Virtual Edition: PDF 2.0 Adoption, PDF/UA-2 Drafting, and Post-COVID Document Workflows

PDF Days Europe 2021 was the first fully virtual edition of the annual PDF Association conference, held online on 17–18 May 2021. Sessions covered the practical state of PDF 2.0 adoption one year after the ISO 32000-2:2020 corrigendum, the early technical drafts of PDF/UA-2, accessibility legislation accelerated by remote work, and document workflow changes driven by the shift to fully digital operations during the pandemic.

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Key takeaways

The first corrigendum to ISO 32000-2:2017 addressed specification errors and ambiguities identified by PDF 2.0 implementors in the three years since publication.
Hybrid working created new urgency around PDF accessibility, forcing organisations to make legacy document libraries accessible without in-person workarounds.
PDF/UA-2 development was well underway, with new structure elements and tighter WCAG 2.1 alignment on the roadmap for eventual publication (achieved in 2024).
PDF/A-3 with ZUGFeRD/Factur-X and XRechnung continued maturing as the solution for hybrid human/machine-readable electronic invoices.
The virtual conference format, now a planned choice rather than a forced adaptation, enabled wider geographic participation than any previous in-person event.

PDF Days Europe 2021 was held virtually in May 2021, organised by the PDF Association. It was the second consecutive fully virtual edition, following the groundbreaking 2020 online-only conference. By 2021 the virtual format was a settled fact rather than a forced adaptation, which allowed organisers to invest more in production quality and to draw attendees from a wider geographic range than any in-person Berlin event had previously reached. The 2021 conference carried several specific technical obligations. The first corrigendum to ISO 32000-2:2017 (PDF 2.0) was available, addressing a set of errors, ambiguities, and clarifications identified by implementors in the three years since publication. PDF/UA accessibility was being shaped by the dual context of the hybrid working transition — which had put massive pressure on organisations to deliver digitally accessible documents — and the ongoing development of what would eventually become PDF/UA-2 (ISO 14289-2:2024). The hybrid working context itself was a background presence throughout the event. Organisations that had successfully converted their document workflows to digital-first during 2020 were now managing the longer-term implications: document accessibility requirements, digital signature infrastructure, and PDF/A archiving for records that now existed only as digital originals rather than scanned paper.

ISO 32000-2 errata: the first corrigendum

The first corrigendum to ISO 32000-2:2017 was an important step in the maturation of the PDF 2.0 specification. The corrigendum process in ISO standards provides a mechanism for correcting errors in a published standard without issuing a full revised edition. For PDF 2.0, the corrigendum addressed: Specification errors — A number of normative text errors had been identified by implementors during the 2018–2021 period. These were cases where the specification text said something that implementors quickly discovered was incorrect or internally inconsistent, leading to interoperability problems. Ambiguities — Several passages in ISO 32000-2:2017 were genuinely ambiguous: reasonable implementors could read the text in more than one way and produce conforming but non-interoperable implementations. The corrigendum resolved these ambiguities by providing clearer normative text. Missing definitions — Some terms and structures used in the specification had been incompletely defined, leaving implementors to rely on context or on the PDF 1.7 Adobe specification to fill gaps. Cross-reference corrections — ISO 32000-2 introduced many new and restructured sections relative to PDF 1.7; some internal cross-references in the published specification pointed to incorrect section numbers. Sessions at PDF Days Europe 2021 reviewed the specific changes in the corrigendum and discussed what they meant for implementations that had already shipped, including whether conformance claims needed updating. The PDF Association's PDF 2.0 errata tracking resource was highlighted as a reference for implementors working through the changes.

PDF/UA in the hybrid working era

The shift to hybrid working created a new urgency around PDF accessibility. Before 2020, many organisations could defer PDF accessibility improvements by relying on staff being physically available to assist colleagues with accessibility needs. Remote-first and hybrid environments removed this option: every document had to stand on its own as an accessible digital artefact. PDF Days Europe 2021 addressed several dimensions of this shift: Remediation at scale — Organisations were confronting existing legacy PDF libraries that had been created before accessibility was a priority. Sessions covered strategies for triaging which documents required full remediation versus automated tagging versus archiving as inaccessible-with-disclaimer. Authoring tool improvements — Microsoft Office's PDF export accessibility had improved significantly through the 2019–2021 period, and sessions covered specific configuration steps to maximise tag quality from Office. Adobe InDesign's export path for PDF/UA compliance was also reviewed. Validation maturity — The PAC (PDF Accessibility Checker) and veraPDF had both matured significantly. Sessions reviewed the specific checks each tool performed and their limitations, with practical guidance on interpreting results in remediation workflows. PDF/UA-2 development status — The working group developing what would become PDF/UA-2 was actively progressing. Sessions provided status updates on the new structure elements being added, the relationship to WCAG 2.1, and the timeline for publication. The eventual publication in 2024 was still three years away at this point, but the broad direction was established.

PDF/A-3 and automated document exchange

PDF/A-3's ability to embed arbitrary file attachments within a compliant archiving container had found its major adoption use case in electronic invoicing. By 2021, several European countries had enacted or were enacting electronic invoicing mandates for government procurement, and PDF/A-3 with embedded XML (ZUGFeRD/Factur-X in Germany and France, XRechnung for German federal invoices) was the established solution. Sessions at the 2021 conference reviewed the practical implementation of PDF/A-3 invoice workflows: The ZUGFeRD/Factur-X standard had reached version 2.1, aligning with the EN 16931 European Invoice Core Data Model. The technical implementation requires embedding the XML invoice file in the PDF/A-3 document with specific /AFRelationship values and XMP metadata additions that declare the invoice profile. Implementations using PDF/A validation tools needed to be aware that standard PDF/A validators would report the embedded XML as permissible under PDF/A-3 but not PDF/A-1 or PDF/A-2. XRechnung — The German national e-invoicing standard for federal administration — mandated the use of XML formats. PDF/A-3 with embedded XRechnung XML was accepted as a valid delivery format for invoices to federal German entities. Sessions reviewed the specific technical requirements for this format combination and validation tooling available from German government sources. The broader takeaway from 2021 sessions was that PDF/A-3's hybrid document model (human-readable PDF, machine-readable embedded data) was finding adoption beyond invoicing in areas like scientific data archiving, engineering documentation, and laboratory report delivery.

Frequently asked questions

What was the first corrigendum to ISO 32000-2?

The first corrigendum to ISO 32000-2:2017 (PDF 2.0) was a formal correction document issued through ISO's corrigendum process to address errors, ambiguities, and missing definitions identified by implementors in the years after the standard was published. Corrigenda are technically separate documents from the standard itself; implementations can claim conformance to ISO 32000-2:2017 with or without the corrigendum corrections. The PDF Association maintains an errata tracking resource that documents known issues and their resolution status for PDF library developers working through these corrections.

What is PDF/UA-2 and how does it differ from PDF/UA-1?

PDF/UA-1 (ISO 14289-1:2012) established the baseline requirements for accessible PDF using the structure and tagging capabilities of PDF 1.7. PDF/UA-2 (ISO 14289-2:2024) is based on PDF 2.0 (ISO 32000-2) and introduces new structure element types (/Aside for tangential content, /FENote for footnotes/endnotes), closer alignment with WCAG 2.1 success criteria, and updated requirements for mathematical content using MathML. Significantly, PDF/UA-2 removes the former /B (basic) conformance level that existed in PDF/UA-1, establishing a single, complete conformance requirement. Documents that were compliant with PDF/UA-1/B may not fully satisfy PDF/UA-2 requirements, particularly around newer structure elements and MathML.

What is XRechnung and how does it relate to PDF?

XRechnung is the German national standard for electronic invoicing, mandated for invoices to federal German public authorities (Bundesbehörden) since November 2020. It defines an XML format based on the European standard EN 16931. When delivering XRechnung invoices as PDF, the PDF/A-3 container format is used — the XRechnung XML is embedded as an attachment within a PDF/A-3 document. The PDF provides the human-readable invoice presentation; the embedded XML provides the machine-readable data required by government procurement systems. Validators must check both the PDF/A-3 conformance of the container and the XRechnung schema conformance of the embedded XML.

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