Archives, courts, and regulators increasingly won't accept a plain PDF. They want PDF/A — the ISO-standardised archival flavour of PDF, designed so a document opens and looks the same decades from now. The difference is self-containment: a PDF/A embeds everything it needs (fonts, colour information) and bans anything that could break over time (external dependencies, JavaScript, encryption).
Converting is straightforward. The part that trips people up is the menu: nine conformance levels with names like PDF/A-2b and PDF/A-3u. This guide covers the conversion and, more usefully, how to pick.
Before you start
- PDF/A can't be encrypted. The standard forbids it, so a password-protected file has to be unlocked before it can become a PDF/A — and you can't password-protect the result afterwards without breaking conformance.
- Know if you were told which level to use. Archives and courts often specify one ("PDF/A-1b" or "PDF/A-2u"). If you've been given a requirement, use it and skip the decision below.
- This is a one-way trip for editing. A PDF/A is meant to be final. You can still convert it back to an editable format later — see PDF to Word — but the archival file itself is a frozen record.
The steps
- Open Blackpdf's PDF to PDF/A tool and drop your file in.
- Choose a PDF/A Version (the nine options are explained below). The default, PDF/A-2b, is the right answer for most people.
- Choose a Colour Profile — sRGB for screen and web documents, CMYK for print-targeted archival, or Grayscale for black-and-white archival. sRGB is the sensible default.
- Click Convert to PDF/A.
- Download the archival file.
Decoding the nine options
The name has two parts: a number (which generation of the standard) and a letter (how strict the conformance is).
The number — what the format allows:
- PDF/A-1 — the original, and the strictest. Maximum compatibility with old systems, but it doesn't allow modern features like transparency or layers. Choose it when an archive explicitly demands PDF/A-1.
- PDF/A-2 — the modern, sensible middle. Supports JPEG2000 compression and layers. This is the default choice for most documents.
- PDF/A-3 — same as 2, but it can also carry embedded file attachments (for example, the original spreadsheet alongside the archived invoice). Only pick this if you actually need to attach source files; some archives reject it precisely because of that ability.
The letter — how strict:
- b (basic) — guarantees the document looks right forever. Visual fidelity only. The easiest bar to clear, and enough for most archiving.
- u (Unicode) — everything in "b", plus text is Unicode-mapped, so the text can be reliably searched and extracted. A good upgrade if the document's text matters.
- a (accessible) — the strictest: everything in "u", plus the document must be properly tagged for accessibility (structure, reading order). Required when accessibility compliance is part of the mandate. Hardest to achieve — it needs a well-structured source document. Our accessibility guide explains tagging.
In short: if nobody told you which to use, PDF/A-2b is the right default. Choose 2u if searchable text matters, 2a if accessibility is required, 1b if you're told to use PDF/A-1, and a 3 variant only if you need embedded attachments.
Common questions
Which PDF/A version should I choose?
PDF/A-2b unless you've been told otherwise. It's modern, widely accepted, and doesn't impose the tagging burden of the "a" levels. Step up to 2u for guaranteed searchable text or 2a for accessibility compliance.
What's the difference between PDF/A-1a and PDF/A-1b?
The letter is the strictness. 1b guarantees the document looks right; 1a additionally requires it to be tagged for accessibility and have a defined reading order. 1a is significantly harder to satisfy and only needed when accessibility is mandated.
Which colour profile should I pick?
sRGB for anything that lives on screen or the web (the common case). CMYK if the archive is print-targeted. Grayscale for black-and-white archival — for instance, a scan you've already converted to grayscale.
Can I password-protect a PDF/A?
No. PDF/A prohibits encryption — a protected file isn't a valid PDF/A. If the document needs both, keep an archival copy and a separate password-protected copy.
Will the file get bigger?
Usually a little, yes. PDF/A embeds fonts and colour profiles that a normal PDF might reference externally, and that self-containment costs bytes. It's the price of the file still opening correctly in twenty years.
My scanned document needs to be a searchable PDF/A.
OCR it first to add a real text layer, then convert to PDF/A-2u, which guarantees that text is Unicode-mapped and extractable.
Wrap-up
- Drop your PDF into PDF to PDF/A.
- Pick the version — PDF/A-2b unless told otherwise.
- Pick a colour profile — sRGB for most documents.
- Click Convert to PDF/A and download.
The whole point of PDF/A is a document that still opens correctly long after the software that made it is gone. For the deeper background on what the standard changes and when it's required, see PDF vs PDF/A.