PDF/A – The format of the future – Part 2: PDF/A-2

PDF creation at the push of a button

As already described in the first part of our blog series, PDF/A - The format of the future - Part 1: PDF/A-1, the PDF/A format (A = Archive) is already used very successfully for archiving data.

The advantages clearly speak in favor of PDF/A as a format, and it is now widely used by companies as well as by public authorities and administrative institutions that must archive documents for years and decades. In short: thanks to ISO certification, PDF/A is an ideal archiving format for government agencies, archives, libraries, publishers, and similar institutions. With the use of the e-case file (electronic records), the PDF/A file format is also becoming more widespread in this area, because it is highly suitable for legally compliant archiving.

Using PDF/A for long-term archiving​

Storing data long-term only makes sense if it can be found and opened again at any time in the future. This requirement for the unconditional reproducibility of a PDF/A document means that all important information must always be contained in the document. This includes text, fonts, and graphics. Readability and visual appearance must remain intact in archived documents so that statutory retention requirements can be met reliably.

After PDF/A was declared a global archiving standard in 2005, additional subformats were developed as further refinements. The PDF/A-1 format (PDF/A-1a and PDF/A-1b) was extended in 2011 by the ISO 19005-2 standard. This introduced the PDF/A-2 format, which is divided into the three conformance levels PDF/A-2a, PDF/A-2b, and PDF/A-2u.

What distinguishes PDF/A-2 and what is it used for?​

The Portable Document Format (PDF) is particularly suitable for long-term archiving, especially for organizations that need to manage large volumes of documents, including emails and attachments. Like PDF/A-1, PDF/A-2 offers exact visual reproducibility and meets accessibility requirements. It also supports JPEG 2000 and very large page formats. JPEG 2000 image compression is important for scanned documents because it can deliver better quality. JPEG 2000 offers lossless compression, which is especially relevant for libraries and archives that want to scan and preserve books or historical documents, such as maps.

Unlike PDF/A-1, PDF/A-2 also allows multiple files to be merged into a container PDF. This can be useful in email archiving, for example when attachments are filed separately from email text. In addition, PDF/A-2 improves support for transparency effects, which matters when the source file is a PowerPoint presentation or a PDF with highlighted text. Another important feature of PDF/A-2 is that layers are allowed, OpenType fonts can be embedded, and digital signatures comply with the PAdES standard.

The PDF/A levels 2a, 2b, and 2u are intended as extensions to PDF/A-1 (PDF/A-1a and PDF/A-1b). This enables long-term archiving with transparent objects, layers, page scaling, and OpenType fonts. In PDF/A-2, these are stored in a central file, which also allows more font capabilities. Data stored with PDF/A-2 remains true to the original and can be reproduced reliably, even after long periods and under different technical conditions.

The subformats PDF/A-2a, PDF/A-2b, and PDF/A-2u differ as follows:​

  • PDF/A-2a: "a" stands for accessible; this level primarily concerns the semantics and structure of the document.
  • PDF/A-2b: "b" stands for basic; this level focuses on exact visual reproducibility and is especially suitable for long-term archiving of images and graphics.
  • PDF/A-2u: "u" stands for Unicode; text is represented in Unicode, enabling reliable display later, including across countries and writing systems through international encoding.

Important: Both PDF/A-1 and PDF/A-2 remain valid even after the introduction of PDF/A-3. While levels 1a and 2a are often sufficient for text archiving, at least level 1b or 2b is recommended for long-term archiving that includes graphics, images, or tables. The PDF/A-2 format described here is mainly used when custom fonts and images are involved, as these are harder to archive in other formats. The current standard format is PDF/A-3. We will cover this format in more detail in Part 3 of our blog series.