What is PDF/A?

PDF/A is a special type of PDF that was designed for long-term digital archiving and preservation of electronic documents. Instead of endless filing shelves and ring binders for paper documents, our modern digital world asks for a method that ensures the easy retrieving and displaying of documents over an extended period of time. In Europe PDF/A is recommended or even legislated for long-term archiving in various organisations and governments. In the US such recommendations exist in the fields of jurisdiction and libraries. They all rely on a preservation that ensures that electronic documents can be reproduced for many years, and in the exact original way, even when using different software.

PDF/A exists in different variants. Each of them is has different PDF/A standards and conformance levels. The PDF/A standards define the features and image compression technologies which help preserving the content of a file. At the same time the PDF/A standard supports different conformance levels. Through these levels, the accessibility requirements that impact the understanding of the content are being controlled. By knowing the different options for PDF/A, you can improve the value of your documents for your viewing, printing, sharing and archiving purposes.

PDF/A-1: This is the originial PDF/A standard and comes with some restrictions regarding the use of fonts, color, annotations, and some other elements. It comes in level b (basic) and level a (accessible).
PDF/A-1b focuses mainly on the preservation of the visual appearance of a document while
PDF/A-1a adds features that improve the file's accessibility for physically impaired users. Its requirements include reliable text semantics and structure information to preserve the document’s natural reading order and logical structure.

PDF/A-2: This standard has several additions like a JPEG 2000 compression and optional content layers, as well as PDF packages. It also allows file attachments, as long as the attached documents themselves conform to PDF/A-1 or PDF/A-2. While PDF/A-2 also comes with level b and level a conformance, a new conformance - level u (unicode) - was introduced. It guarantees that the text can be reliably searched and copied.

PDF/A-3: Part three of the standard is almost identical to PDF/A-2. The only difference is that it allows arbitrary file formats to be embedded into PDF/A conforming files. These arbitrary file formats are CSV, CAD, XML, spreadsheet documents, word-processing documents and more.

None of the different ISO standards replaces their predecessor, and future developments to the PDF/A standard won't make current PDF/A versions obsolete. There is always the requirement that future PDF viewing applications must be backward compatible, which means that older versions of PDF/A will still be displayed correctly.