PDF Standards

PDF/X standards and a practical guide for professional print production.

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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

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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

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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 transparency

When to Use It

• Offset print
• Working with external print shops
• When maximum compatibility is required

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PDF/X-4:2008

Modern Print Standard

 Live transparency
 Accepts CMYK and RGB
 Layer support
 OpenType fonts
 ICC profile

When to Use It

• Digital print
• Designs containing transparency
• Modern workflows
• NowToPrint recommendation

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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

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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 Intent

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Exporting 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)

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PDF Validation

Adobe Acrobat Pro

Tools → Print Production → Preflight
→ Select PDF/X-1a or PDF/X-4 profile
→ Analyse

Online Tools

• PDF24 Tools
• PDF Validator

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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	Browser requests require an authenticated session and CSRF token; request body is capped at 5 MB, batch data at 500 rows, and returned ZIP 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.
Measured native runtime	Public measured-render claims require a current-source Linux manifest V3 bundle, real native smoke, direct PDFium FFI fuzz, ASan/LSan, and an independently signed isolation receipt. Local verifier tests are not runtime evidence.
Browser WASM release	Public browser-engine claims require all four WASM artifacts to share one exact source/provenance identity, source-scope v2, byte hashes, immutable asset versions, committed lineage, and a same-run signed current-HEAD receipt. A local contract test or hand-edited receipt is not release evidence.
Real-world corpus	A public corpus claim requires at least 50 distinct, sanitized, hash-only PDF admissions, independent human Ed25519 review, pinned reviewer keys, multiple source programs, and minimum coverage across five print-product classes. Synthetic fixtures and unsigned local review records do not count.
External oracle matrix	A public differential-oracle claim requires exact-current-HEAD signed receipts from veraPDF, qpdf/libqpdf, PDFium, and mutool over the same 50+ admitted corpus. Each receipt pins executable, lock, command, runner, result-set, log, and offline read-only execution policy, with zero unclassified false-negative or page-count divergence. A configured tool or green workflow alone is not evidence.
Passport report quality	A premium Passport report claim requires an exact-current-HEAD signed child artifact for ar, en, and tr: five pinned HTML/PDF security, visual, tagged-structure, Unicode, and ActualText lanes plus six human receipts across JAWS, NVDA, and VoiceOver on HTML and PDF surfaces. Unit tests, a single screenshot, or unsigned accessibility notes do not count, and this evidence is not PDF/UA certification.

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.

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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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