About PDF to PDF/A
PDF/A is the version of PDF designed for long-term archiving. It's the format museums, libraries, courts, and government archives store documents in when they expect the documents to still be readable in fifty years. Regular PDFs depend on the reader having the right fonts, the right software, sometimes access to external resources online. PDF/A is self-contained: everything the document needs to display correctly is baked in.
PDF to PDF/A converts a regular PDF into the archival format. The output looks identical to the input but it's structured to survive software changes, font deprecations, and the passage of time.
What changes in the conversion
Fonts get embedded. If the source PDF referenced fonts that weren't included in the file (relying on the reader's machine to have them installed), the conversion embeds the actual font data into the PDF/A so it'll render correctly even on a machine that doesn't have the font.
Colour profiles get attached. PDF/A requires an explicit colour profile (usually sRGB for screen documents or CMYK for print-bound documents) so the colours render consistently across viewers.
Encryption, transparency effects, JavaScript, embedded multimedia, and external links are stripped. PDF/A doesn't allow anything that depends on outside resources because the file is meant to be standalone.
Metadata gets restructured into a format that archival systems can index reliably.
PDF/A flavours
PDF/A-1 is the original spec. The strictest, the most widely supported, and the safest pick for documents you genuinely need to preserve forever. Doesn't allow attachments or layers.
PDF/A-2 adds support for layers, attachments, JPEG 2000 images, and digital signatures. More flexible while still meeting archival requirements. Good middle ground for most modern documents.
PDF/A-3 is the most permissive, allowing arbitrary file attachments. Used in industries like accounting and tax where invoices need to carry their source data embedded.
If you're not sure which flavour to pick, PDF/A-2b (the basic conformance level of PDF/A-2) is the right default. It works for almost any document and is accepted by every system that takes PDF/A.
When PDF/A matters
Court filings. Most modern court systems require PDF/A submissions because they need documents that will be openable years into a long-running case.
Government records, tax filings, regulatory submissions. Agencies typically require PDF/A to ensure their archive can be read in the future.
Academic theses and research papers. Universities increasingly require PDF/A so the library copy stays readable.
Long-term business archives. Contracts, board minutes, audit records that need to be retrievable decades later.
What doesn't always convert cleanly
Documents with custom embedded media (videos, audio, 3D models). These get stripped. If the multimedia is essential, PDF/A might not be the right format for that document.
Documents with very unusual fonts that the engine can't fully embed. Most fonts work, but some specialised typefaces with restrictive licensing can't be embedded under the licence terms. The conversion swaps them for the closest available alternative, which sometimes shifts the layout slightly.
Encrypted PDFs. The encryption has to be removed before conversion because PDF/A doesn't allow encryption.
How to verify a PDF/A file
Open the PDF in Acrobat Reader. Click File, then Properties. The Description tab shows the PDF version and the PDF/A conformance level if any. A compliant file shows something like "PDF/A-2b" in the standards information.
Many archival systems run their own validator on incoming files. If your file is rejected, ask the system administrator to share the validator output. The error usually points at a specific issue (missing font subset, missing colour profile, unresolved external reference) that can be fixed with another pass through the converter or a small manual adjustment.
If you need formal validation for a regulatory submission, the open-source veraPDF tool runs a complete spec check and reports every deviation. It's free and reliable. Run your converted file through veraPDF before submission to catch anything the engine missed.