Understanding the PDF/A Standard
PDF/A is the global standard for long-term document preservation. Learn how it works, why standard PDFs fail, and which conformance level you need.
1. The Core Purpose of ISO 19005
Standard PDF files are designed for dynamic document exchange and immediate printing. They often rely on fonts installed on the host operating system, external hyperlink references, embedded JavaScript actions, or proprietary media codecs. Over time, as operating systems update and software dependencies shift, a standard PDF opened 10 years later may render with altered layouts, missing characters, or missing elements.
PDF/A (ISO 19005) guarantees 100% self-containment. Everything required to render the document precisely—fonts, color space profiles, vector paths, and metadata—must be embedded directly inside the file binary.
2. Comparison of PDF/A Standards
| Standard | ISO Standard | Base PDF Version | Key Features |
|---|---|---|---|
| PDF/A-1b | ISO 19005-1:2005 | PDF 1.4 | Basic visual preservation. No transparency or layers allowed. |
| PDF/A-2b | ISO 19005-2:2011 | PDF 1.7 | Supports transparency, layers, JPEG2000, and embedded PDF/A files. Recommended for general business. |
| PDF/A-3b | ISO 19005-3:2012 | PDF 1.7 | Allows embedding non-PDF file attachments (e.g. XML spreadsheets, ZUGFeRD e-invoices). |
3. Prohibited Elements in PDF/A
- Unembedded Fonts: All fonts must be 100% embedded with ToUnicode character mapping tables.
- Device-Dependent Colors: Raw RGB/CMYK values must specify an embedded sRGB or ICC OutputIntent profile.
- Dynamic Code: JavaScript actions and interactive button scripts are barred to avoid operational failures and security risks.
- Audio & Video: Embedded MP3, MP4, or Flash content is prohibited due to codec obsolescence.
- Password Protection: Encryption is barred so future archivists are never locked out of public records.
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