What Is PDF/A?
PDF/A is a specialized subset of the PDF format designed for long-term digital preservation. The "A" stands for "Archival." It is an ISO standard (ISO 19005) that restricts PDF features to ensure that documents remain readable, viewable, and reproducible decades or even centuries into the future — without requiring the original software, fonts, or operating system.
Standard PDF files can include JavaScript, reference external files, depend on system fonts, use encryption that may become unreadable, and embed multimedia that requires specific codecs. All of these dependencies create risk: if any component becomes unavailable, the document may not render correctly. PDF/A eliminates these risks by requiring everything to be self-contained.
PDF/A compliance is legally mandated in many contexts. The European Union requires PDF/A for electronic court filings. The US Library of Congress recommends PDF/A for digital preservation. Many government agencies, healthcare institutions, and financial regulators require PDF/A for official document submissions. Understanding the compliance levels helps you choose the right one for your situation.
The Three Compliance Conformance Levels
Each PDF/A part (1, 2, 3) has three conformance levels:
| Level | Name | Requirement |
|---|---|---|
| a | Accessible | Full structural tagging (headings, lists, tables). Supports screen readers. Most stringent. |
| b | Basic | Visual appearance preserved. No structural tagging required. Most common. |
| u | Unicode | Like level b, plus all text must have Unicode mappings. PDF/A-2 and 3 only. |
In practice, level b is the most widely used because it is achievable from most document types without manual structural tagging. Level a requires the document to have complete semantic structure (like a well-formed HTML document), which most automated converters cannot guarantee.
PDF/A-1b: The Foundation
Standard: ISO 19005-1 (2005), based on PDF 1.4
PDF/A-1b is the most widely accepted and most restrictive version. It is based on PDF 1.4 features only and prohibits:
- JavaScript — No executable code of any kind
- Encryption — No password protection or access restrictions
- External references — All fonts, images, and color profiles must be embedded
- Transparency — No alpha blending or transparency groups
- Audio/video — No multimedia content
- Form fields — No interactive form elements (XFA forms are explicitly prohibited)
- Compression: LZW compression is prohibited; only Flate (DEFLATE) and JPEG are allowed
What must be present:
- All fonts embedded (or subset embedded — only the characters used)
- XMP metadata (document title, author, creation date, modification date)
- ICC color profile (sRGB for screen, CMYK for print) embedded in the file
- PDF/A identification tag in the XMP metadata
Best for: Legal documents, court filings, government submissions, financial records, and any context where maximum compatibility with validation tools is required. PDF/A-1b validators are the most mature and widely available.
PDF/A-2b: The Modern Standard
Standard: ISO 19005-2 (2011), based on PDF 1.7
PDF/A-2b adds features that were missing from PDF/A-1:
- Transparency support — Alpha blending and transparency groups are allowed. This is critical for documents converted from modern word processors and design tools that use transparency extensively.
- JPEG2000 compression — Better image compression than JPEG, producing smaller files at equivalent quality.
- PDF/A attachments — A PDF/A-2 file can embed other PDF/A-1 or PDF/A-2 files as attachments. Useful for bundling related documents.
- OpenType fonts — Full OpenType font embedding (PDF/A-1 only supported TrueType and Type 1).
- Optional content groups — Layers can be included (but must all be visible by default).
Everything prohibited in PDF/A-1b remains prohibited in PDF/A-2b (JavaScript, encryption, external references, multimedia).
Best for: Modern document workflows where transparency is used (presentations converted to PDF, documents with watermarks, layered graphics). PDF/A-2b is the recommended level for new archival projects.
PDF/A-3b: Attachments Unleashed
Standard: ISO 19005-3 (2012), based on PDF 1.7
PDF/A-3b is identical to PDF/A-2b with one major addition: it allows any file type to be embedded as an attachment. PDF/A-2 only allows PDF/A attachments; PDF/A-3 allows Excel spreadsheets, XML data, CAD drawings, source code, or any other file.
This enables use cases like:
- Electronic invoices (ZUGFeRD/Factur-X) — A human-readable PDF invoice with machine-readable XML data attached. The PDF/A-3 container holds both the visual document and the structured data.
- Scientific papers with source data — A published paper with the raw datasets, scripts, and supplementary materials attached.
- Engineering documents — A PDF drawing with the original CAD file embedded for future editing.
The embedded files are not required to be PDF/A compliant themselves — they are treated as opaque data blobs preserved alongside the archival PDF.
Best for: Hybrid documents that combine human-readable content with machine-readable data, electronic invoicing (ZUGFeRD), and scientific publishing with supplementary data.
Choosing the Right Level
| Use Case | Recommended Level | Why |
|---|---|---|
| Court filings (US, EU) | PDF/A-1b | Most validators expect it; maximum acceptance |
| Government archives | PDF/A-2b | Modern standard, transparency support |
| Corporate document retention | PDF/A-2b | Best balance of features and compatibility |
| Electronic invoices (ZUGFeRD) | PDF/A-3b | Required for XML data attachment |
| Healthcare records | PDF/A-1b or 2b | Depends on jurisdiction |
| Academic publications | PDF/A-2b | Transparency for modern layouts |
| Scanned document archives | PDF/A-2b | JPEG2000 for better compression |
When in doubt, PDF/A-2b is the safest modern choice. It is accepted everywhere PDF/A-1b is accepted (since 2b is a superset of 1b's visual requirements) and supports transparency that modern documents frequently use.
How to Create PDF/A-Compliant Files
From Word Documents
Convert your DOCX to PDF with the PDF/A option selected. Our DOCX to PDF converter supports PDF/A output. Ensure all fonts are embedded in the source document first.
From Existing PDFs
Convert standard PDFs to PDF/A by embedding missing fonts, removing prohibited features (JavaScript, encryption), and adding required metadata. Our PDF tools can handle this conversion. The process may fail if the source PDF uses features that cannot be represented in PDF/A (e.g., multimedia, form scripts).
From Scanned Documents
Scanned images converted to PDF are excellent candidates for PDF/A because they are inherently simple — just images on pages. Add OCR text layers to make the content searchable while maintaining visual fidelity. Our PDF OCR tool creates searchable PDF/A output from scanned documents.
Validation
After creating a PDF/A file, validate it with a dedicated tool:
- veraPDF — Open-source, the reference implementation used by most archival institutions. Validates all PDF/A levels.
- PDF/A Pilot — Commercial tool from callas software. Validates and converts.
- Adobe Acrobat Pro — Built-in PDF/A validation (Preflight panel).
- JHOVE — Open-source format validation tool used by digital preservation communities.
A file that claims PDF/A compliance (via its XMP metadata tag) but fails validation is technically non-compliant and may be rejected by systems that verify compliance. Always validate before submission.
Common Issues and Troubleshooting
Font embedding failure. Some fonts have license restrictions that prohibit embedding. The converter will report which fonts cannot be embedded. Solution: substitute with a freely embeddable alternative (e.g., replace Arial with Liberation Sans, or Times New Roman with TeX Gyre Termes).
Transparency converted to flattened objects (PDF/A-1b). Since PDF/A-1b prohibits transparency, the converter must "flatten" transparent elements — compositing them against their background. This can produce visual artifacts, especially on overlapping text and images. If transparency is important, use PDF/A-2b instead.
JavaScript-dependent forms break. Interactive PDF forms that rely on JavaScript for validation, calculations, or conditional logic lose all interactivity in PDF/A. The form fields become static text. If forms are required, consider creating static snapshots of filled forms.
File size increases significantly. Font embedding, uncompressed metadata, and ICC profiles add size. A 1 MB standard PDF may become 2-3 MB as PDF/A-1b. PDF/A-2b with JPEG2000 compression can partially offset this for image-heavy documents.
Color shifts after conversion. PDF/A requires explicit color management (ICC profiles). If the source document lacks a color profile, the converter assigns one (usually sRGB), which can cause subtle color shifts on documents originally created without color management.
Conclusion
PDF/A is a non-negotiable requirement for legal archiving, government compliance, and institutional document preservation. PDF/A-1b is the safest choice for maximum validator compatibility. PDF/A-2b is the modern standard that handles transparency and better compression. PDF/A-3b enables hybrid documents with embedded data files. Always validate your output with veraPDF or an equivalent tool before submitting to archival systems.
Ready to convert? Try our free DOCX to PDF converter with PDF/A support — no registration required.
