Preflighting
The Preflight operation takes the input PDFs for a print asset and validates them against the product's properties. If any correctable errors are found, they can be automatically fixed. The problems preflight fixes are listed below.
Preflight is usually the first operation on any print asset, and its output feeds the remaining operations. It is also the operation most relevant to clients, because its report tells you whether your files are press-ready and, if not, what needs to change.
What can preflight decide?
Every preflight produces one of three outcomes:
- Pass — the files meet the product's requirements; the asset proceeds to production.
- Pass with warnings — the files are acceptable and production proceeds, but the report notes issues worth addressing on future files (for example, an image below the recommended resolution).
- Fail — one or more blocking issues were found. Processing stops, no further operations run, and the report lists the errors so the file can be corrected and re-submitted.
The report is always available, including on failure, so it can be inspected to see the cause.
What does preflight check?
Preflight validates each component (interior, cover, and — where applicable — the jacket) across the following categories. Errors block the asset until corrected; warnings are advisory and don't stop production.
| Category | What it validates | Blocks? |
|---|---|---|
| File integrity | File isn't empty, is under 2.5 GB, and can be opened — no corrupt data or repaired cross-reference table | Error if empty, oversized, corrupt, or otherwise unreadable |
| Security | PDF isn't password-protected or otherwise encrypted in a way that prevents opening | Error if the file can't be opened for processing |
| Dimensions / page geometry | Page boxes exist and are readable; trim size matches the product spec; interior book block pages don't have mismatched sizes when the product doesn't allow mixed dimensions; page coordinates use a standard user unit | Error if a page box is missing/invalid, trim size doesn't match spec, mixed page sizes aren't supported, or user unit isn't 1 |
| Bleed | Content reaching trim has sufficient bleed on bleed-supporting products | Warning if bleed is present but below the required amount |
| Page count | Interior page count is valid for the binding — meets minimum/maximum and any modulus (e.g. multiple of 4 for saddle-stitch) | Error if below minimum, above maximum, or not a valid multiple |
| Cover / spine sheet count | A cover or dust-jacket asset's page count matches what the product expects; interior page count supports the derived spine width | Error if sheet count or spine width don't match |
| Fonts | All fonts referenced by text are embedded | Error if a font isn't embedded |
| Font quality | Type3 fonts are flagged; character codes set by page content resolve to a glyph in their font | Warning for Type3 fonts or unmapped characters |
| Images — resolution | Effective PPI is within the product's supported range | Warning if below the recommended minimum PPI or at/above the high-PPI threshold on both axes |
| Images — rendering intent | Every embedded image declares a rendering intent | Warning if /Intent is absent |
| Vector complexity — node count | Vector node density and count per page stay within limits | Warning if exceeded |
| Vector complexity — object count | Drawing-object density and count per page stay within limits | Error if exceeded |
| Color space | Detected colorspaces are in the product's allowed set; Lab colorspace isn't used on images or vector fills/strokes when disallowed; spot colors carry a usable alternate or tint transform | Error if an unsupported colorspace, disallowed Lab usage, or an undefined spot color is found |
| Color channel count | Total process + unique spot channels don't exceed the product's maximum | Warning if exceeded |
| Transparency | Flags overlapping transparent colors and objects; flags a document declaring both transparency-permitting and transparency-prohibiting PDF/X variants | Warning for live transparency (resolved at the press, not by the customer); Error for mixed variant declarations |
| Interactivity / annotations | No annotations, AcroForm fields, or JavaScript actions | Error if any are present |
| Layers | No default-off layer carries visible content; a dieline layer, if present, is a non-printing spot color | Error for hidden content on an off layer; Warning for an invalid dieline layer |
| White overprint | No white-filled or white-stroked element has overprint enabled in a way that would make it vanish on press | Error if detected |
| PDF metadata | Producer field is present in the document | Warning if missing |
What does preflight fix automatically?
Preflight fixes the problems below itself, and the asset continues to production. RPI prints from the fixed file rather than the one you sent, so these changes appear in the printed book.
| Row in the table above | Problem | What preflight does to the file |
|---|---|---|
| Page count | Too few pages, or a count that isn't the multiple the binding requires | Adds blank white pages at the end until the count is valid |
| Dimensions / page geometry | Trim size doesn't match the product | Rebuilds the page at the product's size, with its content scaled to fill it |
| Dimensions / page geometry | A page box is missing or invalid | Sets the page boxes where the product needs them, cropping an oversized page; the content is not moved or scaled |
| Dimensions / page geometry | Pages of mixed sizes | Clears once the pages have been rebuilt at the product's size |
| Images — rendering intent | An image declares no rendering intent | Gives the image the rendering intent in effect where it is drawn, or Perceptual if none is |
| Color space | Lab color on an image | Re-encodes the image in RGB |
| Color space | Lab color on text or vector shapes | Converts the color to CMYK |
| Interactivity / annotations | Annotations on a page | Removes the page's annotations |
Preflight does not fix anything else in the table above. A page count above the product's maximum, for example, is still an error that blocks the asset until you correct the file and submit it again.