Transparency errors: KDP's unflattened layers and IngramSpark's 'Complex Image' explained

Transparency is anything see-through in your file: a drop shadow, a glow, a soft or faded edge, a shape or line of text set partly see-through, a PNG picture with a see-through background, or layers stacked with special effects. Screens show these easily. A printer's system has to work out what every overlap should look like in ink, and sometimes that goes wrong: the file fails, or prints with odd boxes and lines.

Flattening merges all those layers into one flat picture, so nothing see-through is left.

What the platforms say (as at 4 October 2026)

KDP. Its formatting help warns that unflattened layers and transparency can cause upload errors, and its cover checklist asks you to flatten all transparency. KDP prefers PDF/X-1a, a version of PDF made for printing. PDF/X-1a can't hold live transparency, so exporting to it flattens your file. Heavy transparency can also be behind KDP failing to process an interior at all; see corrupt or locked PDFs.

IngramSpark checks for "File contains transparency" when you upload. Later, its prepress team can return "Complex Image in Interior/Cover PDF File" when artwork or transparency is too complicated to print safely. The fix is to flatten, or rasterise: turn drawn (vector) artwork into an ordinary picture made of pixels. IngramSpark asks for PDF/X-1a:2001 or PDF/X-3:2002 files.

Lulu shows a warning (orange, not a red error) when an element may be transparent. Its PDF settings ask you to flatten transparent layers and vector objects, and to rasterise vector images.

Bookvault's upload check doesn't look for transparency. If every check passes but your file still shows as Failed, Bookvault suggests exporting again as PDF/X-1a or PDF/X-3.

How to fix it in Word

Word adds transparency through effects and some pictures. Remove them one by one.

1. Click each picture. On the Picture Format tab, open Picture Effects and set Shadow, Reflection, Glow and Soft Edges to none.
2. If you've used Picture Format > Transparency on a picture, set it back to no transparency.
3. Click each shape or text box. On the Shape Format tab, set Shape Effects to none, then open Format Shape and make sure Fill and Line transparency are 0%.
4. Select your text and check Home > Text Effects for shadows, glows or outlines. Remove them.
5. Logos and decorations are often PNG files with see-through backgrounds. Open each in a photo program, put it on a white background, save it as a JPEG (which can't hold transparency), then in Word right-click the picture and choose Change Picture > From a File.
6. Save as PDF and run the check below.

Using a designer, InDesign, Affinity or Canva? Export as PDF/X-1a:2001, which flattens transparency. In a photo editor, flatten the image before you save it. If your design tool offers a "flatten" option when you download a PDF, tick it.

Check before you upload

Bervet's free spine width calculator checks interior and cover PDFs, including for transparency and whether the file is PDF/X. The check runs in your browser and nothing is uploaded; checking a PDF needs a free Bervet account.