A file your printing works can put straight on the press

What a print-ready file is, and what it saves you

Send an ordinary PDF to a printing works and somebody there has to open it and check things you never thought about: whether the colours are stated in the inks the press lays down or in the colours of a screen, whether the photograph that reaches the edge of the page reaches a little past it, where the blade is meant to cut, and whether the lettering is inside the file or merely assumed to be on their machine. Every one of those questions is an email, and every email is a day.

A print-ready file carries the answers itself. PDF/X is the published agreement on what a file has to carry to be that file: something a printing works can ask for by name, and something a program can be held to.

Two words come up the moment this is discussed, and both are simple. The ink is run a few millimetres past the edge of the finished page — that overhang is the bleed, and it is there because a stack of paper never cuts twice in exactly the same place. The line the blade follows is the trim. A file stating both leaves nothing to guess.

A job that comes back is not merely late. The sheets already run are waste, the press time is booked a second time, and the date that mattered — a mailing, a trade fair, a notice that has to appear — moves. Getting the file right the first time is the whole of the saving.

Three parts, and they are three different products

PDF/X is not one rule with settings. It is published as ISO 15930, in numbered parts that arrived years apart, and those parts do not ask for the same drawing at all. A file satisfying the oldest one cannot have been drawn the way a file satisfying the newest one is drawn. Choosing between them decides what your pages may contain.

The thing that separates them is what the trade calls transparency: anything on the page that lets what sits under it show through — a shadow beneath a logo, a tint laid over a photograph, wording you can read the text through. The two older parts do not allow any of it to remain in the file.

PDF/X-1a ISO 15930-4:2003

The oldest and the strictest. Nothing on the page may show through anything else, and no colour may be left described as a screen colour: everything is turned into the inks the press will actually lay down before the file is written. A great many traditional printing works still ask for this one by name.

PDF/X-3 ISO 15930-6:2003

The same, with one thing allowed on top: a colour may be described by a colour profile instead of being stated as ink. It is the middle step of the three, and the one asked for least often.

PDF/X-4 ISO 15930-7:2010

The modern one. What shows through stays as it was drawn, and so do layers — the separate sheets of one drawing that can be shown or hidden, such as a second language or the outline of a cut. Nothing is redrawn on the way out: what you drew is what the printing works receives.

We write the modern part, and only that one

The engine writes PDF/X-4. It does not write PDF/X-1a and it does not write PDF/X-3, and we would far rather you read that here than discover it on a deadline.

The reason is not that the older parts are harder to spell. To write one of them a program has to flatten the page: take a place where a shadow sits over a photograph over a tint, work out what every square millimetre of that pile actually looks like, and redraw the whole thing as flat shapes with nothing showing through anything — while keeping the lettering crisp and every colour exactly where it was. That is a second piece of engineering, not a switch inside the first.

So the honest answer is the one on this page. If your printing works asks for PDF/X-4, the engine writes it. If it asks for PDF/X-1a, this is not the tool for that job, and we are not going to pretend otherwise.

On a modern press that is rarely a loss. Keeping what shows through means the printing works flattens the page itself, on its own equipment and at its own fineness, which is later and better than a program on your desk deciding it weeks in advance.

An invoice and a press file are two different documents

The engine also writes electronic invoices — the kind a French or German company must now send, with the figures carried inside the file so that the customer's accounting reads them without anybody retyping anything. Those are made to be kept: they follow the archiving standard, PDF/A-3.

A file is one or the other, not both, and that is not a limit we invented. The archiving standard needs a second file carried inside the first, and the way of carrying it belongs to a later version of PDF than the one the print standard is built on. The people who write the print standard say it plainly for every one of its parts: a file ready for the press carries nothing else inside it.

In practice the question never comes up. An invoice is read on a screen and filed for ten years; a catalogue cover goes on a press. Nobody prints an invoice on an offset press, and nobody files a press sheet with their accounts. Ask for the one the document is for, and the engine writes it.

Four things the engine insists on before it writes anything

A file claiming PDF/X on its cover and not holding up is worse than a file that never claimed it: it goes through, and it comes back. So when a document is asked to claim PDF/X-4, the engine checks four things first, and if any one of them is missing it will not write the file. It stops and names the one that is missing.

1. The colour profile of the press the document is meant for. It has to describe a machine that puts ink on paper: the profile of a screen is turned away, because a screen is not what will print it.
2. A title for the document. Not the name of the file — a title written inside it, which is what every program down the line shows and files it under.
3. An answer on trapping, said as yes or as no and never left blank. Trapping is the hair's breadth of overlap given to two touching colours so that a sheet moving very slightly on the press does not open a white line between them. Whether it has been done is the printer's business to know.
4. The trim line, stated on every page and not on the first one alone. That is the line the blade follows, and a page that does not carry it cannot be cut without somebody ringing you up to ask where.

What nobody can check for free, and what we do instead

Here we have to be plain with you. For documents kept for the long term there is a free, independent checker, veraPDF, and every example we publish goes through it. For PDF/X there is no such thing. veraPDF checks the archival rules and the accessibility ones, and says so itself; the programs that check PDF/X are sold, mostly by the same firms that sell the software producing the files.

So nobody hands you a free certificate on this, and we are not going to imply that somebody has. What holds the claim up is our own checking: the four refusals above, applied to every document, and two further checks that owe nothing to the engine's opinion of itself — a set of rules read off the standard and run over the finished file, and a comparison with a file made by an altogether different program. Those two are being put in place now.

And if your printing works runs its own check on what it receives, as most of them do, that is a third pair of eyes: the one that actually settles the matter on the day.

Where this shows up in your day

If you send anything out to be printed — a catalogue, a run of labels, a mailing, a cover — this is the difference between a proof that comes back right and a week of messages about why it did not. If you never print anything, none of it touches you: the engine writes an ordinary document exactly as before.

It costs nothing extra. It is the same engine, and it is in every offer.

See it on a finished document

A sheet a printing works runs without asking a question A sheet as it goes to the press A file that states the device its colours are meant for Which colour profiles the engine works with

See the prices See the examples