PDF/A - An Overview

PDF/A is a specialized version of the popular PDF format designed specifically for long-term document preservation. The “A” in PDF/A stands for “Archive”, signifying its purpose to ensure that documents are preserved and displayed consistently over time, regardless of changes in software, hardware, or operating systems.

Key features of PDF/A

One of the major advantages of PDF/A is its ability to always render exactly the same, no matter the system or software used for viewing. This is achieved through its unique design principles:

• Self-Contained Files: A PDF/A file is 100% self-contained. This means that all information needed to display the document—fonts, images, color profiles, and any other essential data—is embedded directly in the file itself.

• No Reliance on External Sources: Unlike standard PDFs, PDF/A does not depend on external resources to render the content. This makes it an ideal format for archiving important documents for long-term use.

PDF/A Standards

There are four different version of PDF/A files and each has its own ISO standard. Higher number of the version means that more features are a part of the file format.

PDF/A-1

• Original PDF/A standard, the most restrictive and the most commonly used today.

• Based on PDF 1.4.

• ISO 19005-1

PDF/A-2

• Adds support for transparency, layers, improved image compression and attachments (provided that those attachments are in PDF/A format).

• Based on PDF 1.7

• ISO 19005-2

PDF/A-3

• Permits any file type as attachment.

• Based on PDF 1.7

• ISO 19005-3

PDF/A-4

• Based on newest PDF standard - PDF 2.0.

• ISO 19005-4

PDF/A Conformance Levels

Level B (Basic)

PDF/A-1B, PDF/A-2B, PDF/A-3B

• B-level conformance requires only that documents conform with guidelines for reliable viewing and therefore, is the easiest level to achieve.

Level A (Accessible)

PDF/A-1A, PDF/A-2A, PDF/A-3A

• “Accessible” conformance is a superset of B-level conformance. It adds requirements for information intended to preserve a document’s logical structure, semantic content, and natural reading order.

Level U (Unicode)

PDF/A-2U, PDF/A-3U

• Like ‘level A’, U-level conformance requires character mapping to Unicode.

Level E

PDF/A-4E

• Level E introduces support for RichMedia and 3D type annotations as well as embedded files to create a PDF/A version compatible with modern geospatial, construction, and engineering workflows. (The “E” stands for engineering).

Level F

PDF/A-4F

• Allows file types of any format to be embedded inside PDF.

PDF/A Requirements

A PDF/A compliant file must meet the requirements of the PDF/A standard. Some requirements prohibit certain functions that could hinder long-term archiving, while others guarantee reliable reproduction.

Minimum requirements include:

• All content must be embedded (fonts, colors, text, images, etc.) and must not reference external content

• The file does not contain audio or video (unless PDF/A-4F)

• The file does not contain JavaScript

• The files does not use LZW compression

• The file is not encrypted or password protected

• Metadata in the file is encoded using Extensible Metadata Platform (XMP) technology

• The file does not use XFA forms

• Interactive form fields must have an appearance dictionary

PDF/A Verification

JavaUtils can detect if document is PDF/A-1A or PDF/A-1B. It uses PDFBox preflight which will become deprecated in future, so it is recommended to use veraPDF.

PDFBox preflight, veraPDF and Adobe Pro can verify if document is PDF/A compliant BUT sometimes they can give different results. For example PDFBox preflight (our JavaUtils) says that document is PDF/A-1B compliant but Adobe Pro says it is not.