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· 4 min read
How to Check a PDF Is Ready for Print
Manesh Jayawardhana
CIO & Co-founder
You send the PDF to the printer on Thursday. On Friday they email back: fonts not embedded, images RGB, no bleed. The job slips a week, and every one of those problems was visible in the file before you sent it.
Preflight is the check that catches them, and the four things it looks for account for nearly every rejection.
The four checks that matter
Embedded fonts. If a font isn’t embedded, the printer’s system substitutes another. The substitute has different metrics, so line breaks move, text reflows, and a carefully set page comes out wrong. This is the single most consequential preflight failure because it changes how the document looks rather than just its quality.
Colour space. An offset press works in CMYK. Send RGB and someone’s software converts it — possibly the printer’s, using settings you didn’t choose, and colours can shift noticeably. Many digital presses handle RGB fine, so this depends on the process, but assuming is where it goes wrong.
Image resolution. Effective resolution is what matters: a 300 dpi image scaled up 200% in the layout is effectively 150 dpi. Preflight measures the effective figure, which is often lower than the source file suggests.
Bleed. Anything printing to the edge needs to extend past the trim line, typically by 3mm, because guillotines are not perfectly accurate. Without bleed, a millimetre of drift leaves a white sliver along the edge.
What PDF/A is and when you need it
PDF/A is an ISO standard for long-term archiving. It requires the file to be self-contained: fonts embedded, no external references, no encryption, no embedded video or JavaScript, and explicit colour management.
Many legal, government and institutional archives require it. It’s a different question from print readiness, though the two overlap heavily — a PDF/A conformant file has embedded fonts by definition.
| Check | Fails when | Consequence |
|---|---|---|
| Fonts | Not embedded | Text reflows on the printer’s system |
| Colour | RGB where CMYK expected | Colour shift, uncontrolled conversion |
| Resolution | Effective dpi below target | Soft or pixelated print |
| Bleed | No bleed box, art to edge | White slivers after trimming |
Common mistakes to avoid
- Fixing problems by editing the PDF rather than the source document, which patches symptoms and often creates new ones.
- Checking resolution on the source images rather than the effective resolution after scaling in the layout.
- Assuming “export as PDF” from a design application produces a print-ready file — the export preset determines nearly everything.
- Adding bleed to the artboard but not extending the artwork into it.
- Treating a preflight pass as a proof. Preflight checks technical conformance, not whether the design is correct.
How to do it with PDF Preflight Validator
The PDF Preflight Validator reads the file in your browser and reports what a printer or archive would object to.
- Upload the PDF and choose the profile matching its destination — commercial print, or a PDF/A archive level.
- Read the failures in order, starting with unembedded fonts.
- Fix at source in the design file, then re-export and re-check.
- Ask your printer for their preferred export settings; most publish them and following them prevents most of these problems.
The PDF Association publishes accessible explanations of the PDF/A levels if you need to pick one. Other PDF tools are in the tools directory.
Frequently asked questions
Why do fonts need embedding?
Because a system without that font substitutes another, and the substitution changes metrics — line breaks move and the layout shifts. It’s the preflight failure that alters the document rather than just degrading it.
What is PDF/A and when do I need it?
An ISO-standardised subset of PDF for long-term archiving: self-contained, no external dependencies, no scripts. Many legal and government archives require it.
Is RGB always wrong for print?
No. Many digital presses accept RGB and convert well. An offset workflow expecting CMYK will convert without your input, and that’s where colour shifts appear.
Final thought
Run preflight before you send, and fix problems in the source document rather than the PDF. A patched PDF passes the check and frequently fails the press.