PDF guides
PDF/A-1 vs PDF/A-2 vs PDF/A-3: Which Do You Need?
PDF/A comes in several parts and conformance levels, and “PDF/A” on its own is not enough to say what a submission requires. This guide compares PDF/A-1, PDF/A-2 and PDF/A-3, explains the a, b and u levels, and shows which version the PDF to PDF/A tool produces and why.
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The parts of the standard
| Part | Published | Based on | Notable difference |
|---|---|---|---|
| PDF/A-1 | 2005 | PDF 1.4 | The original; no transparency, no JPEG 2000 |
| PDF/A-2 | 2011 | PDF 1.7 | Allows transparency, JPEG 2000 and layers; can contain other PDF/A files |
| PDF/A-3 | 2012 | PDF 1.7 | Same as part 2, but can also embed files in any format |
| PDF/A-4 | 2020 | PDF 2.0 | Newer, built on the current PDF version |
What the letters a, b and u mean
- b (basic): the visual appearance of the pages can be reliably reproduced. This is the minimum level.
- u (Unicode): b, plus every character maps to Unicode so text can be searched and copied reliably. Available in parts 2 and 3.
- a (accessible): u, plus a tagged logical structure so assistive technology can read the document. Tagging must already exist or be added deliberately; it cannot be invented by a converter.
Which one does Looty Tools create?
PDF to PDF/A creates PDF/A-2b only. Part 2 is a sensible modern default: it is based on PDF 1.7, so it preserves transparency and modern image formats that PDF/A-1 would force a converter to flatten or reject. The b level is the one a conversion tool can honestly produce from an arbitrary PDF, because levels u and a depend on information the source file may not have.
That means the tool does not satisfy a requirement that names PDF/A-1b, PDF/A-3, or an “a” level. It says what it makes so you can compare it against the requirement.
How to choose
- Read the requirement. If it names a specific part and level, use exactly that.
- If it just says “PDF/A” with no version, PDF/A-2b is usually accepted, but confirm with whoever is receiving the file.
- If you must attach source data such as an XML invoice payload, you are looking at PDF/A-3, which this tool does not create.
- If accessibility is required, you need an “a” level, which starts from a properly tagged source document rather than a conversion.
PDF/A-1 vs 2 vs 3 FAQ
- Is PDF/A-2 backward compatible with PDF/A-1?
- Not automatically. A PDF/A-2 file can use features that PDF/A-1 forbids, so it is not guaranteed to pass as PDF/A-1. Submit the part the requirement names.
- Is PDF/A-3 “better” than PDF/A-2?
- It is not a newer replacement; it is part 2 plus the ability to embed arbitrary files. Choose it only if you need that.
- Why is only the “b” level offered?
- Because b can be achieved by converting an existing PDF, while u and a require Unicode mappings and tagged structure that a conversion cannot reliably create.
- What about PDF/A-4?
- PDF/A-4 is built on PDF 2.0 and is newer, but it is not what this tool creates. If a requirement names it, this tool is not the right fit.
- How can I check which level a file claims?
- The file’s metadata declares a part and conformance letter, and a validator such as veraPDF checks the file against that claim.
Related guides
- What Is PDF/A?What the PDF/A archival standard actually requires — embedded fonts, defined color, no encryption or scripts — who asks for it, when an ordinary PDF is enough, and why validation matters.
- Why PDF/A Conversion FailsThe real reasons a PDF cannot become a valid PDF/A-2b file — encryption, damage, fonts that cannot be embedded, scripts and attachments — and a practical sequence of fixes to try.
