The proof came back wrong. Now what?
Something is wrong with it. That is normal, and it is what the copy was for.
The useful skill is not spotting the fault — you already did that, it is sitting on your desk. It is naming the cause correctly, because most proof faults have exactly one cause and a boring, specific fix. Guessing costs you another proof and another week of shipping.
Find your symptom below.
The cover is darker and flatter than it looked on screen
Cause: none. This is the medium. A monitor emits light; paper reflects it. Every printed cover comes back darker and less saturated than the file, and deep blues, near-blacks and subtle gradients lose the most.
Do not change anything on the strength of a mild difference. You are comparing a backlit object with a reflective one, and no file edit closes that gap.
Act only if it is severe: the title is sinking into the background, or an area you designed as detail has gone to solid mud. The fix then is to lift the brightness and contrast of the artwork itself, not to re-shoot or re-generate it. Raising the mid-tones and pulling the type further from the background in value usually recovers a cover that "printed black."
The title is not centered on the spine
Cause: the page count or the paper changed after the cover was built. The spine width is computed from the real page count, the paper color and the printer. Change any of the three and the cover you already exported is the wrong width, so the artwork wraps a little to one side and the spine text follows it.
The arithmetic is small and ruthless. On KDP, white stock bulks 0.002252 in per page and cream 0.0025 in. A 300-page book is 0.676 in on white and 0.750 in on cream — 0.074 in of difference, and half of that lands on each side of the fold.
The fix: rebuild the cover from the final page count and the paper you actually ordered. Do not nudge the title sideways to compensate, which fixes one copy and breaks the wrap.
A white sliver along one edge
Cause: no bleed, or artwork that stopped at the trim line. Trimming has a tolerance. If the art ends exactly where the blade is meant to fall, some copies come back with a hairline of bare paper and others do not.
Standard bleed is 0.125 in past the trim on every outside edge. There is no bleed at a spine fold — the fold is interior to the sheet. Extend the artwork, re-export, and check that nothing important moved into the extra 0.125 in.
In the Cover Maker. It draws live trim, bleed and safe-area guides while you work, and computes the spine from the real page count, paper color and printer, so a rebuild after a page-count change takes a minute rather than an afternoon. Start a book → · about the Cover Maker
Text disappears into the gutter
Cause: the inside margin is too small for the page count. A thick book pulls more paper into the curve of the binding than a thin one, so a gutter that was generous at 180 pages is tight at 400.
Use the total inside margin by page count: up to 300 pages, 0.5 in; 301–500, 0.625; 501–700, 0.75; 701–828, 0.875; beyond that, 1.0. KDP's own floor is 0.375 in and IngramSpark's is 0.5 in, so building to 0.5 is valid at both. Widen the gutter, re-pour, and expect the page count to move — which sends you back to the spine.
Images look soft or muddy
Cause: resolution below the print target at printed size. The target is 300 DPI at the size the image appears on the page, not at the size of the original file. An image that is 300 DPI at 2 in wide is 100 DPI when you run it across 6 in.
The fix is a larger source file. Failing that, print it smaller: halving the printed width doubles the effective DPI. Enlarging pixels you never had adds size, not detail, and a resampled 150 DPI photograph still prints as a soft photograph.
A page printed in color you did not expect
Cause: an image or an element that is not quite neutral. Black-and-white interior printing wants black ink only. A scan with a faint warm cast, a logo in a near-black that is really a mix, a chart in muted blues — each is enough to push that page, and sometimes the whole book, onto color pricing.
Convert every interior image to true grayscale and check that headings and rules are black ink, not a rich black built from several inks.
The spine text wraps onto the front cover
Cause: the spine is too narrow for the type. Reduce the spine type size, shorten what you put there — title and last name is enough — or accept that some books do not get spine text at all. KDP prints spine text only above 79 pages, so an 80-page book has a spine of roughly 0.18 in to work with on white stock.
Blank pages in odd places
Two causes, and only one is a fault. A blank verso so the next chapter opens on a right-hand page is correct typesetting, and you should leave it. A stray blank in the middle of a chapter is a manual page break left in the manuscript. Find it in the source document and delete it there, not in the PDF.
The whole book is thicker or thinner than you expected
Cause: paper. Same page count, different stock, different object. Cream is thicker than white per page, and printers differ from each other more than they differ within themselves: Lulu computes bulk as pages ÷ 444 plus 0.06 in for glue, while IngramSpark follows a curve off its own templates — about 0.00209 in per page for white between 100 and 338 pages, and about 0.00192 between 338 and 700.
Nothing is broken. But if you switch printer or paper later, the cover has to be rebuilt.
The rule
Fix the file, order another proof, and never approve a proof you have only looked at on screen. Second proofs are routine; plenty of books go to three. The alternative is a print run of the thing you decided to live with.
Make yours
Everything here is built into the tools, and they are free to use: name your book, bring your manuscript or your artwork, and work as long as you like. You only pay when you want the files without the preview watermark.
Next: The proof checklist, front to back · More: Order the proof. Then read it in daylight · Preflight: what to check before you upload · How to calculate spine width · Margins and gutters