A file prepared to go to 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 a list of things: 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 fonts are 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.

The ink is run a few millimetres past the edge of the finished page, which is the bleed, because a stack of paper never cuts twice in exactly the same place. The other line is the one the blade follows. 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

It is published in numbered parts, and those parts do not ask for the same drawing at all. A file satisfying the oldest one cannot have been created the way a file satisfying the newest one is created. Choosing between them decides what your pages may contain.

What separates them is transparency: a shadow beneath a logo, a tint laid over a photograph, wording you can read the picture through. The newest part carries all of it into the file as it was drawn; the two older ones ask for a page where every mark is opaque.

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. Older printing works still ask for this one by name; a modern one rarely does.

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 layers 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.

The part the engine writes today, and the two that are coming

The engine writes PDF/X-4, the modern part. PDF/X-1a and PDF/X-3 are planned for a future version.

The reason is not that the older parts are harder to write. To write one of them a program has to flatten the page first, and doing that well — keeping the letters crisp and every colour exactly where it was, wherever a shadow sits over a photograph over a block of plain colour — is a second piece of engineering, not a switch inside the first.

So: if your printing works asks for PDF/X-4, the engine writes it today. If it asks for one of the two older parts, write to contact@hqf-pdf.com and the team will tell you where that work stands.

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. 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 no other file inside it.

An invoice is read on a screen and filed to stay readable decades from now; a catalogue cover goes on a press. 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 if any one of these is missing, the engine stops and names it.

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. You are not expected to know it: ask your printing works, and copy their answer across.
4. The line the blade follows, stated on every page and not on the first one alone. A page that carries it is a page the guillotine can cut without anybody ringing you up to ask where.

Who checks a file claiming this, and with what

For documents kept for the long term there is a free, independent checker, veraPDF, and every archival document goes to it before a change enters the library or the service. For PDF/X there is no such thing: the programs that check it are sold, mostly by the same firms that sell the software producing the files.

What holds the claim up is the four refusals above, applied to every document before it is written, and two further checks run over the finished file. Eleven rules read off the standard are put to veraPDF as a policy of its own, one verdict per rule; and the same page is written a second time by Ghostscript, an altogether different program, and ten points of structure are compared.

Both of those are ours rather than the checker's: veraPDF reads the file and applies the rules we wrote from the published text. The page about the checker says exactly where that line falls.

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 the first sample off the press coming 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 The free checker, and what it does decide The fine points of this standard, and what is still being checked

See the prices See the examples