in Production
Always order a proof copy
A screen shows you the file. A proof shows you the book. The difference is where most expensive mistakes hide.
Before a book is printed in quantity or released for sale, there is a step that is easy to skip and expensive to regret: ordering a physical proof and checking it properly.
What a proof catches that a screen does not
A PDF on screen shows the file. A proof shows what the printer does with it, on the actual paper, with the actual cover finish, bound at the actual size. Several kinds of problem only become visible at that point.
Colour is the most obvious. A screen cannot show exactly how ink will look on a particular paper. Covers can print darker or duller than expected, skin tones shift, and dark images can fill in and lose detail.
Scale is another. Type that looked comfortable on screen may be too small or too large in the hand. Margins may feel cramped. The inner margin in particular can turn out too narrow, with text disappearing into the gutter.
Physical fit is a third. The spine may be slightly wider or narrower than the cover allowed for, so spine text drifts towards the front or back. Elements close to the edge may be trimmed closer than expected.
Paper matters too. Show-through from the other side of a thin page, a paper colour that makes images look muddy, or a cover finish that picks up fingerprints are all better discovered before thousands of copies exist.
Kinds of proof
Printers offer different proofs. A digital proof is a PDF, sometimes marked up by the printer, which is useful for checking layout but not colour or paper. A print-on-demand proof is usually a copy made on the same process and materials as the finished book, which makes it a very good guide. For offset printing, printers may offer digital prints of the cover and pages for checking colour and imposition, or, at greater cost, a wet proof made on the press itself.
Whichever is used, the proof should be as close as possible to the real thing.
How to check a proof
Look at it first as a reader would. Hold it, open it, read a few pages in ordinary light. Is it comfortable? Does it look like the book it is meant to be?
Then check it systematically. Look at the cover in daylight and under artificial light. Check the spine alignment and read the spine text from a shelf's distance. Scan the barcode with a phone app to make sure it returns the right ISBN. Go through the interior page by page: page numbers, running heads, chapter openings, blank pages, images and the inner margin.
Give the front and back matter particular care: the title page, copyright page, contents and any index. These pages are often assembled late in the process and are easily overlooked.
When to order another
If the proof shows problems, correct the files and order another proof. It feels like a delay. It is much less of one than reprinting a run or withdrawing a book from sale.
A proof is also a last chance to catch errors in the text, but it should not be the first time the text is proofread. Checking a proof for production problems and proofreading the words are different tasks, and each deserves its own pass.