Book printing: what the printer expects from your files

Most book printing problems do not originate at the printer — they originate in the files sent there. A typeface was substituted with something else, images came out blurry, the cover was trimmed in the wrong place, or the spine ended up two millimetres too narrow. Every one of these is usually discovered once the run is already boxed.

This article covers what a print-ready file contains, what the terms in a printer's specification actually mean, and which mistakes end up costing the most.

Print-ready PDF — what that means

Printers today almost always expect a PDF, often in the PDF/X-1a or PDF/X-4 standard. This is not an ordinary "print to PDF" — it is a standard that guarantees the file contains everything necessary and nothing dangerous.

A print-ready PDF has:

• all fonts embedded in the file, not referenced;
• the correct colour space — the body usually single-colour (black) or CMYK, never RGB;
• bleed and trim marks;
• images at print-quality resolution;
• the correct page order — as single pages, not spreads (unless the printer asks otherwise).

The body and the cover are supplied as separate files. The cover is one wide sheet containing the back cover, spine and front cover together.

Bleed and safe area

Bleed is the extension of colour or image past the trim line — usually 3 mm, sometimes 5 mm. Why: a stack of paper is cut in one pass and the blade always drifts by a fraction of a millimetre. Without bleed you get a white sliver along the edge.

Safe area is the opposite rule: text and important elements must stay at least 5 mm inside the trim line, and more on the inner edge. Binding swallows part of the page — the thicker the book, the more.

If an image is meant to reach the edge of the page, it must be designed with bleed. If it stops short of the edge, no bleed is needed. The most common mistake is designing the image at exactly page size — then you have neither.

Colour: CMYK, RGB and why the screen lies

A screen is a light source and uses RGB; print is a reflective surface and uses CMYK. CMYK has a narrower gamut, which is why bright blues, neon greens and saturated oranges always come out duller in print than on screen.

Practical rules:

• Body text should be 100% black (K), not a black mixed from four inks. Four-colour black text comes out fuzzy at the edges because four plates are never perfectly aligned.
• Large solid black areas on a cover need the opposite treatment — a rich black — or they look greyish.
• A Pantone colour is used when a brand needs an exact tone. It is a separate plate and means extra cost.
• If the book is black and white, make sure no page accidentally contains colour. A single RGB image in the middle of the body can turn the whole job into four-colour printing — and multiply the price.

Image resolution

For print the requirement is 300 dpi at final size. That means: if an image goes into the book 100 mm wide, it needs roughly 1,200 pixels of width.

An image made for the screen is typically 72–96 dpi and cannot be rescued by enlarging — missing information cannot be conjured up. If no originals exist, the only solution is to place the image smaller.

When scanning photographs and documents, scan at 400–600 dpi right away, especially if the originals are small or you plan to enlarge them. With old photographs, scanning is a one-off job you do not want to repeat.

Diagrams, charts and logos are best supplied as vectors (PDF, EPS, AI) — they stay sharp at any size.

Paper, binding and spine width

Paper. The body is usually printed on 70–100 g/m² offset paper (for text — slightly cream and comfortable to read) or on coated paper (for images — smoother and more contrasty). Fiction almost always gets offset paper; photo books get coated. Very thin paper lets text show through.

Binding.

• Perfect binding (softcover) — the most common and cheapest, suitable from about 60 pages.
• Section-sewn binding — pages are sewn in signatures. More expensive, but the book opens properly and does not fall apart. Justified for substantial, long-lived works such as reference books.
• Saddle stitching — only for thin publications, up to roughly 40–60 pages.
• Hardcover — more expensive, but the choice for libraries and gift editions.

Spine width is calculated from the page count and paper thickness. The printer will give you the formula or calculate it — ask for it before designing the cover. If the page count changes during layout, so does the spine.

Signatures. A book is printed on large sheets folded into signatures of 8, 16 or 32 pages. That is why page counts are always multiples of 8 or 16. If the manuscript yields 203 pages, the typesetter either tightens slightly or adds blank leaves. A good typesetter accounts for this at the start of the job.

Digital or offset printing

Digital printing needs no plates, so it is cheaper and faster for small quantities. Sensible up to about 200–300 copies. It also suits reprints and print-on-demand.

Offset printing requires plate-making, but after that each copy is cheap. It becomes worthwhile from around 300–500 copies and gives more even colour and better quality on large areas.

A practical tip: ask the printer for a quote on three run sizes at once (say 100, 300 and 500). The per-copy difference is usually surprisingly large and makes the decision for you.

The proof copy — the one step you must not skip

Before ordering the run, ask the printer for a proof copy or at least a digital proof. On paper the eye notices things a screen never shows:

• whether the type size is genuinely readable;
• whether images are too dark (print always comes out darker than the screen);
• whether the inner margin is sufficient or text disappears into the binding;
• whether the spine sits in the right place;
• whether transparencies and shadows came out as intended.

A proof copy costs tens of euros. A reprinted run costs thousands.

The most expensive mistakes

1. No bleed — a white sliver at the page edge across the entire run.
2. Images in RGB or at 72 dpi — blurry print or an unexpected colour-printing invoice.
3. Fonts not embedded — the printer's machine substitutes something else and the whole layout shifts.
4. Spine width calculated from the wrong paper — the title is off-centre on the spine.
5. Proofreading done only before layout — layout creates new errors that nobody checked.
6. Page count not a multiple of the signature — the printer adds blank leaves where you would not want them.

All of these are preventable, and all of them are preventable only before printing.

Summary

A printer does not fix files — it prints exactly what was sent. That makes print preparation the most consequential part of a typesetter's job: in practice it is a checklist that is the same every time, and skipping it is expensive every time.

We hand over finished print files that meet the printer's specification and, when needed, deal with the printer directly. If your manuscript is ready, see what the work includes on the book design and layout page — or first read through how a book is published step by step.