A file can look flawless on screen and still disappoint once printed. The text suddenly sits too close to the spine, the photographs lose sharpness, the black turns grey, and a thin white strip appears along the edge of the cover. Sometimes the problem surfaces before printing and ends in corrections, another round of file transfers and a shifted deadline. It is worse when it is spotted only once the print run is finished.
Good preparation of a book print file therefore means more than saving the document as a PDF and sending it to the printing house. You have to check the format, the margins, the bleeds, the fonts, the colours, the resolution of the artwork, the page numbering and the construction of the cover. Each of these elements affects the appearance of the book, and some of them also affect its legibility and the way it is bound.
We will show you which mistakes in print files appear most often, and how to catch them before the document reaches the press.
The file looks good on screen. Why is that not enough?
A monitor shows a design in conditions completely unlike paper. The image is backlit, the colours seem more intense, and the zoom can be changed with a single click. On a printout you can no longer zoom in on small text or recover detail that was never in the source artwork.
The differences concern proportions as well. On screen it is easy to miss that the text sits a few millimetres from the trim line, or that a page number has crept towards the edge. Only once the book is bound does it turn out that the inner margin is too small and part of the content hides in the spine.
This is why professional preparation of a book for print calls for looking at the design as a physical object. The book will be trimmed, folded, glued or sewn. Paper has thickness, and every binding method imposes its own limits.
Missing bleeds, or a white strip along the edge
A bleed is the part of the artwork extending beyond the final page size (the trim size) that is intended to be cut away. At Books Factory the bleed in the inside block should be no smaller than 3 mm.
Why add something that will not be visible afterwards? Trimming does not happen with fraction-of-a-millimetre accuracy. Paper can shift slightly during production. If a coloured background, a photograph or an illustration ends exactly on the format line, even a small shift will reveal a white edge.
Bleeds are needed everywhere an element runs to the edge of the page:
- on covers,
- with photographs stretched across a full page,
- with coloured backgrounds,
- with illustrations running out of frame,
- on section pages with full-area printing.
The most common mistake is adding a white strip beyond the format. A bleed should be an extension of the artwork or the background, not an empty margin.
Margins that are too small and text disappearing into the spine
A margin is not empty space to be reduced so that more content fits. It is the safety margin — the area inside the trim size within which all the essential content has to fit. Bleed and safety margin therefore work in opposite directions: the bleed extends beyond the format and will be cut away, while the safety margin lies inside the format and protects the text from being trimmed off or swallowed by the spine.
The inner margin matters most of all. Once the book is bound, part of the page sits close to the spine and does not lie completely flat. If the text has been set too close to the centre, the reader will have to force the book open to see a whole sentence.
The problem grows with the number of pages. A thick publication usually needs a larger inner margin than a slim volume. The construction matters too: a thread-sewn block opens wider than a glued one, and a hardcover behaves differently from a softcover or an integrated binding. The harder the book is to open flat, the larger the inner margin you have to plan for.
The safe area should cover not only the body text, but also:
- page numbers,
- running heads,
- footnotes,
- photo captions,
- boxes and tables,
- logos and small decorative elements.
One of the more frequent mistakes in book printingis setting every margin to the same value. In a book the inner and outer margins have different jobs, which is why they should not always be identical.
The wrong page format
The format of the document has to match the format of the finished book. It sounds obvious, and yet printing houses keep receiving files prepared in A4 although the publication is meant to be A5, B5 or a non-standard size.
Scaling a finished layout to another format affects:
- the size of the text,
- the proportions of the margins,
- the weight of the rules,
- the size of the illustrations,
- the width of the tables,
- the appearance of the whole layout.
If we scale a document down from A4 to A5, the font becomes smaller as well. Text that looked legible on screen may end up too small after scaling.
The format has to be settled before typesetting begins. This applies to page orientation, the way bleeds are counted and the construction of the cover as well. Changing it later usually means re-flowing the text, different paragraph breaks, shifted illustrations and a changed page count.
Pages set as spreads instead of singles
A book is often designed in spread view, because it is easier to control the layout of the left and right pages that way. The finished book print file, however, should usually contain single pages in the correct order, not two pages joined on one sheet.
Imposition, that is the arrangement of pages on the printing sheet, is handled by the printing house. The arrangement depends on the paper format, the press, the folding method and the binding. Preparing sections yourself without agreeing it first can only make production harder.
Fold-out elements or illustrations running across the centre of a spread are the exception, but even then the technical requirements have to be agreed with the manufacturer.
When exporting we also check the order of the pages. The first page of the block is a right-hand page. Blank pages, vacats and title pages have to be present in the file if they are part of the design. The number of pages in the block has to be even — if it is not, a blank page will be added at the end of the block, and that can disrupt the planned ending of the book. The printing house should not have to guess where the author meant to leave a blank leaf.
RGB colours instead of CMYK
A screen emits light, paper reflects it. That is why artwork prepared on a monitor works in RGB space, while a book is produced in CMYK. In print the image is built from ink or toner in the four CMYK colours, which the paper reflects. The range of colours a monitor can display is wider than the range that can be reproduced on paper.
The most intense blues, greens, pinks and neons may become calmer, darker or less saturated after conversion. This is not a fault of the press or an error on the printing house’s part, only the difference between two ways of creating colour.
How should you prepare a print file when the book contains photographs and illustrations? The material has to be converted in line with the profile indicated by the printing house — at Books Factory it is best to prepare the file in the Coated FOGRA 39 profile, and black-and-white material in Gray Gamma 1.8 or 2.2 — and then to check how the colours have changed.
Simply switching the mode from RGB to CMYK is not always enough. The colour profile, the type of paper and the printing method all matter. The same colour will look different on white coated paper than on cream uncoated paper.
For books in which colour matters a great deal, it is worth ordering a proof copy — on the target paper and in the target binding. Even a calibrated screen will not show you exactly how the ink will behave on the chosen substrate.
Black text built from four colours
Black can be built in several ways in print. Body text should normally be prepared as pure black, that is 100% K with no admixture of cyan, magenta and yellow. If small letters are built from four colours, even a minimal registration shift creates a coloured fringe around them and the so-called ghosting effect — the letter loses its sharpness. The text will lose sharpness and look worse than simple single-channel black. Composite black, also called rich black, is made up of several CMYK components and works well on large areas, backgrounds and heavy graphic elements. It should not, however, find its way automatically into every black element.
When preparing files for the printing house, we therefore check more than whether the text looks black. You have to see which colour values it was really built from.
The risk grows when text has been brought over from a word processor. Automatic conversion from RGB to CMYK usually turns black into a composite of four components — so after importing text, tables and charts it is worth checking the components and restoring pure 0/0/0/100 black.
Resolution of photographs and illustrations that is too low
Artwork downloaded from the internet may look good on a monitor and turn out blurred, jagged or full of visible pixels once printed. It all depends on its actual resolution at the target size.
Photographs should have an effective resolution of no less than 300 dpi at the scale at which they will be used in the book — this requirement applies at Books Factory as well. It is not enough, however, to type the value 300 dpi into the file settings. If the image has few pixels, no software will recover the missing detail.
An example? A small photograph from the internet can be labelled as 300 dpi, but stretched across a full page it will still be of poor quality. What counts is the number of pixels and the target print dimension.
Problems also arise with:
- screenshots,
- logos saved as small JPG files,
- images copied out of presentations,
- illustrations enlarged beyond their original size,
- artwork compressed by messaging apps.
Logos, icons and line drawings are best supplied in vector format. That way they can be scaled without losing sharpness.
Fonts that disappear or change their appearance
The font used in a design is not always installed on the printing house’s computer. If it has not been embedded in the PDF or converted to outlines where that is justified, the software may substitute another one for it.
A change of font affects more than the shape of the letters. It can also change the width of the text, the line breaks, the page count and the position of the headings. A single missing typeface can throw a whole layout apart.
Correct PDF preparation for print should include checking that the fonts are embedded. It is also worth making sure that the licence for a given typeface allows it to be used in a printed publication.
Converting the whole book to outlines is not always the best way out. It can increase the file size considerably and make later corrections harder. Embedding the fonts correctly during export is usually enough.
We pay particular attention to fonts used in single places only, for example in an ornamental chapter title, a caption or a quotation. They are easy to miss during a check.
Lines that are too thin and text that is too small
What is visible at high magnification on screen will not always survive printing. Very thin lines can disappear, break up or look uneven. For vector objects — tables, charts, boxes — the safe minimum is 0.25 pt, that is 0.088 mm. This applies particularly to light elements, fine boxes, charts and technical illustrations.
A similar problem arises with small text. A small type size on a dark background, a thin typeface or low contrast can seriously reduce legibility. White text set in a thin font over a photograph is especially risky.
Do not assume that because something is visible in a PDF at 200% magnification it will be equally legible on paper. A design has to be judged at its target size, ideally on a test print.
Mistakes in page numbering
Duplicate numbers, one page missing, a reversed order or a number on a page that was meant to stay blank — problems of this kind often appear after the final corrections.
Changing a few paragraphs can shift the whole layout. Removing an illustration affects the page breaks, and adding a vacat changes the numbering of the rest of the book. If the numbers were typed in by hand instead of using the software’s automatic functions, the risk of error grows.
Before sending the file we check:
- the continuity of the numbering,
- the position of the numbers on left- and right-hand pages,
- the absence of numbers on pages where they should not appear,
- the agreement of the table of contents with the actual numbers,
- internal cross-references,
- footnotes and the index.
Some pages may carry no printed number while still being counted. This often applies to the title page, the imprint page and chapter openings. A missing visible number has to be told apart from a page missing from the numbering.
Typos and proofreading after typesetting
Proofreading the text alone before typesetting does not close the job. Once the book is set, mistakes can appear that were not there before:
- single letters stranded at the end of a line (so-called runts),
- incorrect word division,
- headings left at the bottom of a page,
- single lines of a paragraph carried over to the next page,
- word spacing that is too wide,
- shifted captions,
- tables running beyond the margin,
- repeated or omitted passages.
This is why preparing a book for print should end with a proofread of the typeset pages. It is best to check the file in single-page and spread view, and to print part of the publication at 1:1 scale.
Paper reveals problems quickly that a screen gives no sign of. Font size, line length and the density of a page are perceived differently once printed.
How to calculate the spine width and prepare the cover?
A book cover does not consist of a front and a back alone. You have to allow for the spine, the bleeds, the creasing lines and, with some bindings, the flaps, turn-ins or other technological areas.
The width of the spine follows from the number of leaves (that is the pages divided by two), the thickness of a single leaf and the construction of the binding. The page count alone is not enough: the same block on volume paper will give a noticeably wider spine than on dense paper of the same grammage.
One of the more frequent mistakes is designing the cover before the block has been finally closed. If the page count changes later, the spine width changes with it. The title may stop sitting in the centre, and artwork running between the parts of the cover will shift in relation to the fold lines.
It is best to obtain the cover dimensions from the printing house once you have settled:
- the format of the book,
- the final page count,
- the type and grammage of the paper,
- the binding type,
- the gluing or sewing method,
- whether there are flaps.
Instead of calculating the spine yourself, it is worth using the materials prepared by the printing house — at Books Factory you will find them in the print-file preparation guides for the individual bindings, and the printing calculator will work out the spine width automatically.
Text and barcode too close to the trim line
A cover often carries a great many elements: the title, the author’s name, the blurb, a logo, the barcode with the ISBN, the price, the publisher’s mark. In a small format, space runs out quickly.
Even so, texts should not be pushed right to the edge. The trim can shift slightly, and an element placed too close to the edge will look uneven or be partly cut off.
The barcode also needs an adequate size, contrast and empty space around it. Placing it on a heavily patterned background or distorting its proportions can make scanning difficult.
The spine calls for similar attention. On very thin books the title may not fit on it, or may end up too close to the fold line. Sometimes it is better to leave it out than to print text that will run over onto the front or back cover.
Transparencies, shadows and special effects
Graphics software lets you apply shadows, transparencies, blending modes and all kinds of filters. Not every effect, however, will be processed correctly in a print file, especially if the export was made with the wrong settings.
Problems may involve:
- shadows that disappear,
- rectangular fields around transparent objects,
- changed colours,
- white lines between parts of the artwork,
- incorrect overprint,
- elements that look different once flattened.
Very delicate tints and gradients also call for caution. Values that are too light can disappear in print, and smooth tonal transitions can settle into visible banding. The safe minimum is 5% of the largest colour component; with wide gradients, adding subtle noise helps.
The safest course is to use the PDF standard indicated by the printing house and to check the separations preview and the overprint. With more elaborate designs it is a good idea to ask for a technical check before the whole print run is started.
The wrong PDF standard
Not every PDF is a print-ready file. A document saved from a word processor may contain active comments, form fields, links, layers, unsuitable fonts or artwork compressed far too heavily.
The foundation is a single-layer, clean PDF with embedded fonts. Some printing houses additionally expect compliance with a particular PDF/X variant — it is worth checking this in the specification instead of assuming. Such a standard restricts some of the elements that could behave unpredictably during production.
Before exporting it is worth checking:
- the trim size and the bleeds,
- the way the pages are exported,
- the embedding of the fonts,
- image compression,
- the colour profile,
- that no printer’s marks have been left in the block file,
- the PDF standard,
- the overprint settings,
- the presence of unnecessary layers.
We add printer’s marks only when the manufacturer requires them — at Books Factory they should be removed from the block file. More marks does not mean a better prepared file, only more work for the DTP department.
Not complying with the requirements of the particular printing house
The biggest mistake is often preparing a file according to general principles without checking the specification of the place that is to print the book.
Printing houses can differ in:
- the bleed they require,
- the colour profiles they accept,
- the way black is to be prepared,
- the PDF standard they expect,
- printer’s marks,
- the minimum line weight,
- the construction of the cover,
- the way files are to be delivered.
Well-prepared files match the requirements of a specific production process. Our print-file preparation guides — separate ones for softcover, hardcover and saddle-stitched binding — are worth opening before typesetting begins, rather than only when the finished publication is exported.
If anything is unclear, ask your order manager. A few minutes spent settling the parameters saves hours of corrections later on.
How to prepare a print file without missing the details?
Before sending it, it is worth running the check in several stages. We do not check everything at once, because a single mistake is then easy to overlook.
The construction first
We check the format, the page count, the order, the vacats, the bleeds and the margins. We make sure the pages are single and that all the elements fit within the safe area.
Then the content
We go through the numbering, the table of contents, the footnotes, the headings, the captions, the word division and the places where the layout could have fallen apart after the last corrections.
Next the artwork and the colours
We check the resolution, the colour space, the profile, the transparencies and the overprint, the thin lines and the way the black has been prepared. It is worth looking at every image at its target size.
The PDF file last
We check the embedding of the fonts, the page format, the bleeds, the saving standard and the export parameters. We open the finished PDF in software other than the one the design was made in. That makes it easier to spot problems the source application does not show.
Checklist before sending a book to the printing house
Before handing over the files we check:
- that the format of the document matches the order,
- that elements running to the edge have bleeds,
- that the text is a safe distance from the trim and the spine,
- that the pages have been exported singly,
- that the page count is correct,
- that the artwork has adequate resolution,
- that the colours have been prepared in line with the requirements,
- that small text is built from pure black,
- that the fonts are embedded,
- that the numbering and the table of contents agree,
- that the file contains no comments or stray objects,
- that the cover was built on the current template,
- that the spine width allows for the final page count and the paper,
- that the barcode has the right proportions,
- that the file meets the specification of the chosen printing house.
A good file saves corrections, time and nerves
Correct preparation of a book print file begins much earlier than the PDF export. The format, the paper, the binding and the printing method are worth settling before typesetting. That way the margins, the cover, the artwork and the page count match the finished publication from the outset.
A book, after all, is not a document viewed on a monitor. It is meant to reach the reader’s hands, open well, keep the print sharp and look exactly as planned. Careful checking of the files makes that result possible without frantic corrections at the last stage.
Before you start typesetting, check the technical requirements for the binding you have chosen — you will find them in our knowledge base on file preparation.