PDF Versions and PDF/A Explained
Most PDFs today are version 1.4–1.7 and open everywhere. Special sub-standards exist for specific jobs: PDF/A for long-term archiving, PDF/X for professional printing and PDF/UA for accessibility.
The main PDF versions
| Version | Year | Notable additions |
|---|---|---|
| 1.0–1.3 | 1993–1999 | Basics: text, images, links, then digital signatures |
| 1.4 | 2001 | Transparency. Still a common “safe” choice |
| 1.5–1.6 | 2003–2004 | Better compression (object streams), 3D, AES encryption |
| 1.7 | 2006 | Became ISO 32000-1 in 2008. The most common version today |
| 2.0 | 2017/2020 | ISO 32000-2. Cleaner spec, AES-256 only, better accessibility |
In practice you rarely need to care: any up-to-date reader opens all of them. Version issues mainly appear with very old software or strict upload portals.
Sub-standards for special jobs
PDF/A — archiving
PDF/A guarantees a file can be displayed exactly the same way decades from now. To achieve that it:
- requires all fonts to be embedded,
- forbids encryption, JavaScript, audio/video and external links to content,
- requires colour information to be defined precisely.
Governments, courts, universities and libraries often require PDF/A. Variants include PDF/A-1b, PDF/A-2b and PDF/A-3 (which allows attached files, used by e-invoices such as ZUGFeRD/Factur-X).
PDF/X — printing
Used by print shops. It ensures colours (CMYK), bleed areas and fonts are print-ready.
PDF/UA — accessibility
Ensures a PDF can be read by screen readers: proper tags, reading order, alt text for images.
How to create a PDF/A
- Microsoft Word: File > Save As > PDF > Options > tick PDF/A compliant.
- LibreOffice: File > Export as PDF > tick Archive (PDF/A, ISO 19005).
- Adobe Acrobat Pro: use the Standards or Preflight tool.
Frequently asked questions
How do I check which version a PDF is?
In Adobe Acrobat Reader open File > Properties; the Description tab shows the PDF version. In macOS Preview use Tools > Show Inspector.
Does a government portal asking for PDF/A mean a normal PDF won't work?
Often, yes. Courts, tax offices and archives may reject uploads that aren't valid PDF/A. Microsoft Word can save directly as PDF/A via Save As > PDF > Options > 'PDF/A compliant'.
Is PDF 2.0 widely supported?
Yes, modern readers open PDF 2.0 files, but most software still creates 1.7 files because they are universally compatible.
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