Transparency and layers

What live transparency is

Modern design tools let objects be partly see-through: a drop shadow, a soft glow, a photograph faded into a background, a PNG with a transparent edge. In a PDF these can be stored as live transparency, which the printing system has to calculate when it rasterises the page.

KDP's guidelines recommend flattening transparency before export. Live transparency can print differently from how it looked on screen — with unexpected boxes, colour shifts or missing effects — and those problems often appear only on the printed proof.

Flattening, in practice

In an image editor, merge or flatten the layers and export a single-layer JPEG, TIFF or PNG with no alpha channel. In a layout tool, use a PDF/X-1a export preset, which flattens transparency as part of the standard, or flatten the affected objects manually.

Flatten at full resolution. A flattened image exported at a lower resolution than the original throws detail away for good.

Transparent areas on a cover

A cover image with transparent regions is a special case. Nothing prints in a transparent area — the result is bare paper, which is rarely what was intended. When a panel is left empty in this app's cover builder, it is filled white rather than left transparent for this reason. If you want white, make it white in the artwork.

Checking for transparency before upload

Acrobat Pro's Output Preview can highlight transparent objects on each page, and PDF/X-1a validation fails on any live transparency, which makes the export preset a check as well as a fix. If you cannot inspect the file directly, look for the usual sources: drop shadows, glows, feathered edges, blend modes such as multiply, and PNG images with soft edges.

Text deserves particular care. A transparent effect applied to a text frame can cause the flattener to convert nearby text to outlines or images, which prints slightly heavier than the surrounding text. Keep effects away from body copy, and order a proof when a page combines text with transparent artwork.