PDF Standards
PDF/X standards and a practical guide for professional print production.
PDF Standards
PDF/X standards and a practical guide for professional print production.
What is PDF/X?
PDF/X is a print-optimised PDF standard defined by ISO. Its differences from a regular PDF:
- All fonts embedded
- Colour profile defined
- Transparency rules specified
- Sufficient resolution
PDF/X Versions
| Standard | Year | Feature |
|---|---|---|
| PDF/X-1a:2001 | 2001 | CMYK, most compatible |
| PDF/X-3:2002 | 2002 | RGB + CMYK |
| PDF/X-4:2008 | 2008 | Live transparency, layers |
| PDF/X-5:2010 | 2010 | External references |
| PDF/X-6:2020 | 2020 | PDF 2.0 production exchange |
PDF/X-1a:2001
Most Widely Used
The gold standard for offset print:
CMYK or Spot colour only
All fonts embedded
Flattened content expected for legacy workflows
ICC profile required
No RGB
No live transparencyWhen to Use It
- Offset print
- Working with external print shops
- When maximum compatibility is required
PDF/X-4:2008
Modern Print Standard
Live transparency
Accepts CMYK and RGB
Layer support
OpenType fonts
ICC profileWhen to Use It
- Digital print
- Designs containing transparency
- Modern workflows
- NowToPrint recommendation
Preserve-first policy
NowToPrint checks PDF/X, output intent, transparency, spot colour, and font evidence without silently converting RGB or spot colours to CMYK, flattening transparency, trapping, or outlining fonts. If a conversion is required, prepare and upload a corrected source PDF from a specialist prepress workflow.
Comparison
| Feature | PDF/X-1a | PDF/X-4 |
|---|---|---|
| Transparency | Flattened | Live |
| Colour | CMYK/Spot | CMYK/RGB/Spot |
| Layers | ||
| Compatibility | Very high | High |
| File size | Can be large | Generally smaller |
Exporting from Adobe InDesign
PDF/X-1a
File → Export → Adobe PDF (Print)
Preset: [PDF/X-1a:2001]
General:
Optimize for Fast Web View
Output:
Color: Convert to Destination
Destination: ISO Coated v2 (ECI)
Advanced:
Fonts: Subset 100% (embedded)PDF/X-4
File → Export → Adobe PDF (Print)
Preset: [PDF/X-4:2010]
General:
Create Acrobat Layers
Output:
Color: No Conversion + correct Output IntentExporting from Adobe Illustrator
File → Save As → Adobe PDF
Preset: PDF/X-1a:2001 or PDF/X-4:2010
Marks and Bleeds:
Trim Marks
Bleeds: 3 mm (all sides)PDF Validation
Adobe Acrobat Pro
Tools → Print Production → Preflight
→ Select PDF/X-1a or PDF/X-4 profile
→ AnalyseOnline Tools
NowToPrint Requirements
| Area | Current guardrail |
|---|---|
| Minimum PDF version | PDF 1.4 |
| Recommended format | PDF/X-4 |
| Most compatible | PDF/X-1a |
| Design JSON export | Default guard allows up to 200 design pages; the production JSON request body limit is 15 MB. |
| Batch PDF requests | Request body is capped at 5 MB, batch data is capped at 500 rows, and the returned ZIP is capped at 50 MB. |
| Rust PDF generation | 100 generated pages is the default and hard cap, with hard caps for blocks, table rows, text, Rust objects, and bytes. |
| Large-file streaming | Streaming work is engine-safety and future-flow groundwork, not a public blanket upload-size promise. |
PDF/X evidence in PDF Tools is a standards-readiness signal, not third-party certification. The report checks the available metadata, output intent, transparency, colour, font, geometry, and render evidence and routes uncertain jobs for review.
Common Errors
| Error | Consequence | Solution |
|---|---|---|
| Font not embedded | Font substitution | Embed fonts |
| RGB image | Colour shift | Prepare for print at source, or verify the RIP plan |
| Low resolution | Pixelation | Use 300 DPI |
| Missing bleed | White edge | Add 3 mm bleed |
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