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PDF formats explained

PDF/A explained: when you need an archive copy

PDF/A is a version of PDF designed for long-term storage. If an archive, court, university or records team asks for it, an ordinary PDF may be refused. This article explains what PDF/A is, how to tell whether a file conforms, and what RedactNinja's Prepare PDF/A does.

RedactNinja guide. Updated 5 October 2026.

What PDF/A is

PDF/A is defined by the international standard ISO 19005. The PDF Association describes it as a format that preserves the static visual appearance of electronic documents over time, independent of the tools and systems used to create, store or display them.

In practice, a PDF/A file has to contain everything needed to show it, and must avoid features that depend on outside resources or on particular software. The aim is that the file looks the same when it is opened years from now as it does today.

The parts and conformance levels

The letters matter. Level b (basic) is about reliably reproducing how the pages look. Level u adds the requirement that all text has Unicode equivalents, so it can be searched and copied reliably. Level a (accessible) also requires the document's logical structure, which helps screen readers and text extraction. If you are asked for PDF/A, find out which part and level.

What PDF/A requires and forbids

According to the Library of Congress format description, the PDF/A family requires:

Who asks for PDF/A

Archives and libraries are the most common source of the requirement. The Library of Congress lists PDF/A as a preferred format for textual works, and its format description gives examples from national archives, courts, government departments and universities that recommend or require it for theses and deposited documents.

Records managers also use it for documents that must be kept for many years. Whoever asks for it, their own rules are what count, so follow the part, level and file naming they specify.

How to check that a file conforms

Saving a file as PDF/A, or seeing PDF/A in its properties, does not prove that it conforms. A file can claim to be PDF/A and still break the rules. The reliable test is a validator: software that checks the file against every requirement of the chosen part and level.

veraPDF is a purpose-built, open source validator covering all PDF/A parts and conformance levels. It is supported by the PDF software developer community and designed for digital preservation work. If the recipient names a particular validator, use that one. Keep the validation report with the file if your records process requires evidence.

What RedactNinja's Prepare PDF/A does

PDF to PDF/A prepares a PDF/A-2b candidate in your browser. After you confirm that the document's colours are suitable for sRGB, it adds an sRGB output intent, replaces the catalogue XMP metadata, removes the document information dictionary from the trailer and creates a new file identifier. Page content and the original objects are kept, and the tool checks this before offering the download.

It refuses files it cannot handle safely rather than changing them silently. That includes encrypted PDFs, signed PDFs, files that already have an output intent, forms, attached files, scripts and actions, and fonts that are not embedded. In our test, a simple letter that used a standard font without embedding it was refused with the message that a font is not embedded. A converted report with embedded fonts was prepared without problems.

The download is called a candidate for a reason. The tool does not validate it, does not convert colours, does not substitute fonts, and says that original metadata may remain in unreferenced objects. Validate the candidate with veraPDF or the recipient's validator before you describe it as PDF/A. The tool can also match a RedactNinja validation summary (a JSON file recording a veraPDF pass) to the exact candidate by its SHA-256 fingerprint, but the browser does not check that the summary is genuine.

When you need an archive copy

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