Preflight has 23 checks in six categories. A profile turns each one on or off, gives it a severity and sets its thresholds. The presets turn on the checks that matter for their kind of work; the pages below describe every check with its settings and its value in each preset.
| Category | Checks | Page |
|---|---|---|
| Images | resolution | Image, text and line checks |
| Text and fonts | fonts, text size, small text in several inks | Image, text and line checks |
| Lines | line width | Image, text and line checks |
| Colour and ink | colour spaces, ink coverage, overprint, spots, transparency, registration, tints | Colour and ink checks |
| Page, bleed and safety | bleed, safety margin, page size, page count | Trim, bleed and document checks |
| Document | JavaScript, comments and forms, encryption, PDF version | Trim, bleed and document checks |
Every check#
| Check | Category | What it looks for | Fix |
|---|---|---|---|
| Image resolution | Images | Effective resolution of every placed image at the size it prints (pixels per inch). | Downsample images |
| Fonts embedded | Text and fonts | Every font the file uses must be embedded, or the printer substitutes another one. | – |
| Minimum text size | Text and fonts | Visible text smaller than the press can hold. Reverse (knockout) text can have its own limit. | – |
| Small text in several inks | Text and fonts | Small text built from several process inks blurs when the plates misregister. Rich black (black plus other inks) is the usual culprit. | – |
| Minimum line width | Lines | Artwork strokes thinner than the press can hold. Zero-width lines print as the thinnest line a device can make and can vanish. | – |
| Overprint | Colour and ink | Objects set to overprint print on top of the colours beneath instead of knocking them out. | – |
| White overprint | Colour and ink | White objects set to overprint disappear on press. | – |
| Transparency | Colour and ink | Opacity, blend modes, soft masks and transparency groups. They need a PDF/X-4 capable workflow or flattening. | – |
| Spot colours | Colour and ink | The spot inks in the file: expected ones present, no unexpected, duplicate or inconsistent ones. | – |
| Colour spaces | Colour and ink | Images, text, vector artwork, gradients and transparency blending in colour spaces the press does not print directly, such as RGB. | – |
| Total ink coverage | Colour and ink | The highest sum of process inks anywhere in the artwork (averaged over 0.5 mm), measured from the separations. | – |
| Technical lines overprint | Colour and ink | Die, crease and other technical lines must overprint. Knocking out, they leave white lines in the printed artwork. | – |
| Black overprint | Colour and ink | Solid black text and thin black lines should overprint, so misregistration cannot show a halo around them. | – |
| Registration colour | Colour and ink | Registration colour prints on every plate. It belongs on marks outside the trim, not in the artwork. | – |
| Lightest tint | Colour and ink | Tints lighter than the press's smallest dot drop out or print unevenly, typically on flexo. | – |
| Bleed | Page, bleed and safety | Artwork that touches the trim (or the die outline) must continue into the bleed, and the page boxes must describe it. | Set page boxes |
| Safety margin | Page, bleed and safety | Text too close to the trim or die outline can be cut off or look unbalanced. | – |
| Page size | Page, bleed and safety | The trim size (TrimBox, else the visible page) against the ordered size; pages of mixed sizes. | – |
| Page count | Page, bleed and safety | The number of pages against the order, or a multiple for booklets. | – |
| JavaScript | Document | Scripts in the document, its pages, links or form fields. Print files must not contain any. | Remove comments, forms and scripts |
| Comments and form fields | Document | Comments, markup and form fields sit on top of the artwork and may or may not print. | Remove comments, forms and scripts |
| Encryption | Document | Encrypted files may refuse printing or editing in prepress tools. | Remove encryption |
| PDF version and output intent | Document | The PDF version, and whether the file declares its print condition (a PDF/X output intent). | – |
Severity#
Each check has a severity in the profile: Error, Warning or Info. Its findings take that severity, so the same problem can fail a report under one profile and only warn under another. A few findings keep a severity of their own whatever the profile says, because they are always that serious or that harmless:
| Finding | Severity |
|---|---|
| An image below the Error below resolution of Image resolution | Error |
| An image above the Flag above resolution | Info |
| A zero-width line, when Zero-width lines are errors is on (Minimum line width) | Error |
| No die or cut line ink, when Spot colours requires one | Error |
| Pages of mixed sizes (Page size with no size set) | Info |
| A page that is itself a transparency group (Transparency) | Info |
| "This check could not run" | Warning |
Settings#
Settings are numbers, on/off switches, lists of ink names or a choice. Sizes are in points (9 pt is about 3 mm; see Units and measurements), resolutions in pixels per inch and coverage in percent. A setting of 0 turns that part of a check off where the check says so, such as Error below 0 for no error level.
Some settings must agree with each other. On Image resolution, Error below may not be higher than Warn below, and Warn below may not be higher than Flag above (each only when both are set above 0). The profile editor says which setting needs attention when you save.
What every check skips#
The checks look at the artwork, not at the rest of the page: content wholly outside the product and its bleed (slug, marks, colour bars), hidden layers, registration colour, and technical and finishing inks are left out where they aren't artwork. See what counts as artwork. The document checks (fonts, JavaScript, encryption and the others) look at the whole file.
If one check stops on a problem with the file, the report says "This check could not run" for it as a warning, and the other checks still run.