veraPDF

Also called PDF/A validator

veraPDF is the open source industry reference implementation for checking PDF/A conformance. It is the tool that answers the one Factur-X requirement you cannot see by opening the file: whether the container genuinely satisfies PDF/A-3.

Licence: Open source
Checks: PDF/A conformance, all parts and levels
Where we run it: Our backend, as an opt in per file
Why not in the browser: Structural checks over the whole PDF object graph

Why this check needs a server

The EN 16931 rules are Schematron over XML, which compiles down to something a browser can run. PDF/A conformance is a different kind of problem: hundreds of structural checks over the PDF object graph, fonts, colour spaces and metadata.

That is why our validator splits the two. The XML rules run in your browser and the invoice never leaves it. The PDF/A check runs on our backend through veraPDF, as an opt in you press per file, and the report says which of the two you have run.

What a failure here usually means

Almost always that the file was produced by embedding XML into an ordinary PDF rather than into a PDF/A-3. The result looks identical on screen and is not a conformant Factur-X file.

Fonts are the second most common cause: PDF/A requires them embedded, and a generator that relied on a system font produces a file that renders correctly on the machine that made it.

Why it matters

It is the only way to answer the PDF/A-3 question, and that question is one of the three things a Factur-X file must satisfy.
It is also the reason the deeper check on our validator uploads the file, which we would rather say plainly than bury.

Check it on your own file

Run the PDF/A-3 check
Opt in per file. The browser side pass covers the XML and the embedding, not this.

Common questions

How do I check if a PDF is really PDF/A-3?: Run it through a PDF/A conformance checker such as veraPDF. It is not visible by opening the file, and embedding XML into an ordinary PDF does not make it PDF/A-3.