ISO Standards

phpdftk supports every major PDF subset standard — 7 ISO specifications plus ZUGFeRD, covering 31 conformance levels. Each is validated end-to-end in CI with dedicated integration tests and external tool verification via veraPDF, Matterhorn Protocol, and JHOVE.

The pdf-conformance package validates documents against these standards at write time via PdfWriter::setConformance() or at read time via ConformanceChecker.

Key files:

ConformanceProfile — interface all profiles implement
ConformanceChecker — read-side validation entry point
ConformanceValidator — runs constraints against a document
ProfileConstraintRegistry — maps profiles to constraints
ConformanceXmpWriter — auto-injects XMP identification metadata

At a glance

Standard	ISO	Profiles	PDF Version	Purpose
PDF/A	19005 (Parts 1–4)	11 levels	1.4–2.0	Long-term archival
PDF/UA	14289 (Parts 1–2)	2 levels	1.7–2.0	Universal accessibility
PDF/X	15930 (Parts 4, 6–9)	6 levels	1.3–1.6	Print production
PDF/VT	16612 (Parts 2–3)	3 levels	2.0	Variable/transactional printing
PDF/E	24517-1	1 level	1.6	Engineering documents
PDF/R	23504-1	1 level	2.0	Raster image transport
Factur-X	ZUGFeRD/Factur-X	6 levels	1.7	European e-invoicing
PDF/mail	23053-2	1 level	2.0	Email-safe documents

PDF/A — Long-Term Archival

ISO 19005 (Parts 1–4) ensures documents remain readable decades from now by eliminating external dependencies.

Profile enum: PdfAProfile

Profiles

Case	Part	Conformance	PDF	Tagged	Transparency
`A1a`	Part 1 (ISO 19005-1)	Level A	1.4	Required	Prohibited
`A1b`	Part 1 (ISO 19005-1)	Level B	1.4	—	Prohibited
`A2a`	Part 2 (ISO 19005-2)	Level A	1.7	Required	Allowed
`A2b`	Part 2 (ISO 19005-2)	Level B	1.7	—	Allowed
`A2u`	Part 2 (ISO 19005-2)	Level U	1.7	—	Allowed
`A3a`	Part 3 (ISO 19005-3)	Level A	1.7	Required	Allowed
`A3b`	Part 3 (ISO 19005-3)	Level B	1.7	—	Allowed
`A3u`	Part 3 (ISO 19005-3)	Level U	1.7	—	Allowed
`A4`	Part 4 (ISO 19005-4)	—	2.0	—	Allowed
`A4e`	Part 4 (ISO 19005-4)	Level E	2.0	—	Allowed
`A4f`	Part 4 (ISO 19005-4)	Level F	2.0	—	Allowed

What gets enforced

All fonts must be embedded with complete glyph programs
No encryption permitted
XMP metadata with pdfaid identification required
OutputIntent with ICC profile required
Device-dependent color spaces trigger warnings
JavaScript, Launch, Movie, Sound actions prohibited
LZW compression prohibited (A-1 only)
Transparency prohibited (A-1 only)
Tagged structure required (Level A only)

Constraints

Constraint	Source	A-1	A-2	A-3	A-4
FontEmbedding	`FontEmbeddingConstraint.php`	✓	✓	✓	✓
Encryption	`EncryptionConstraint.php`	✓	✓	✓	✓
Metadata	`MetadataConstraint.php`	✓	✓	✓	✓
OutputIntent	`OutputIntentConstraint.php`	✓	✓	✓	✓
ColorSpace	`ColorSpaceConstraint.php`	✓	✓	✓	✓
Action	`ActionConstraint.php`	✓	✓	✓	✓
EmbeddedFile	`EmbeddedFileConstraint.php`	Prohibited	Prohibited	Allowed	Allowed
Transparency	`TransparencyConstraint.php`	Prohibited	—	—	—
Filter	`FilterConstraint.php`	LZW prohibited	—	—	—
TaggedStructure	`TaggedStructureConstraint.php`	Level A only	Level A only	Level A only	—

use Phpdftk\Pdf\Conformance\Profile\PdfAProfile;

$writer->setConformance(PdfAProfile::A2b);

Tests

PdfA1bIntegrationTest.php — A-1b end-to-end
PdfALevelsIntegrationTest.php — A-1a through A-4f

PDF/UA — Universal Accessibility

ISO 14289 ensures documents are accessible to users of assistive technologies.

Profile enum: PdfUaProfile

Profiles

Case	Part	PDF
`UA1`	Part 1 (ISO 14289-1)	1.7
`UA2`	Part 2 (ISO 14289-2:2024)	2.0

What gets enforced

Complete tagged structure (StructTreeRoot, StructElem hierarchy)
Document language (/Lang) required
DisplayDocTitle must be true in ViewerPreferences
All pages with annotations must have /Tabs /S
Annotations must have /Contents for accessibility (Widget/Popup exempt)
All fonts embedded
XMP metadata with pdfuaid identification

Constraints

Constraint	Source	Applies
FontEmbedding	`FontEmbeddingConstraint.php`	All
Metadata	`MetadataConstraint.php`	All
TaggedStructure	`TaggedStructureConstraint.php`	All
DisplayDocTitle	`DisplayDocTitleConstraint.php`	All
TabOrder	`TabOrderConstraint.php`	All
Annotation	`AnnotationConstraint.php`	All

use Phpdftk\Pdf\Conformance\Profile\PdfUaProfile;

$writer->setConformance(PdfUaProfile::UA1);

Dual profile — combine with PDF/A for archival + accessible:

$writer->setConformanceProfiles([PdfAProfile::A2a, PdfUaProfile::UA1]);

Tests

PdfUaIntegrationTest.php — UA-1/UA-2 end-to-end

PDF/X — Print Production

ISO 15930 ensures reliable color reproduction in print workflows.

Profile enum: PdfXProfile

Profiles

Case	ISO Part	PDF	Transparency	Reference XObjects
`X1a2003`	ISO 15930-4	1.3	Prohibited	—
`X32003`	ISO 15930-6	1.3	Prohibited	—
`X4`	ISO 15930-7	1.6	Allowed	—
`X5g`	ISO 15930-8	1.6	Allowed	Supported
`X5pg`	ISO 15930-8	1.6	Allowed	Supported
`X5n`	ISO 15930-9	1.6	Allowed	Supported

What gets enforced

OutputIntent required (GTS_PDFX type)
TrimBox or ArtBox required on every page
/Trapped must be True or False (not Unknown)
All fonts embedded
No encryption
Transparency prohibited for X-1a and X-3
Reference XObject support validated for X-5

Constraints

Constraint	Source	X-1a/X-3	X-4	X-5
FontEmbedding	`FontEmbeddingConstraint.php`	✓	✓	✓
Encryption	`EncryptionConstraint.php`	✓	✓	✓
Metadata	`MetadataConstraint.php`	✓	✓	✓
OutputIntent	`OutputIntentConstraint.php`	✓	✓	✓
TrimBox	`TrimBoxConstraint.php`	✓	✓	✓
Trapped	`TrappedConstraint.php`	✓	✓	✓
Transparency	`TransparencyConstraint.php`	Prohibited	—	—
ReferenceXObject	`ReferenceXObjectConstraint.php`	—	—	✓

use Phpdftk\Pdf\Conformance\Profile\PdfXProfile;

$writer->setConformance(PdfXProfile::X4);

Tests

PdfXIntegrationTest.php — X-1a, X-3, X-4, X-5g end-to-end

PDF/VT — Variable & Transactional Printing

ISO 16612 (Parts 2–3) builds on PDF/X-4 for high-volume variable data printing (bills, statements, direct mail).

Profile enum: PdfVtProfile

Profiles

Case	ISO Part	PDF	Base
`VT1`	ISO 16612-2	2.0	PDF/X-4
`VT2`	ISO 16612-2	2.0	PDF/X-4
`VT2s`	ISO 16612-3	2.0	PDF/X-4

What gets enforced

All PDF/X-4 constraints plus:

DPartRoot required (document part hierarchy for variable records)
XMP pdfvtid identification

Constraints

Inherits all PDF/X-4 constraints plus:

Constraint	Source
DPartRoot	`DPartRootConstraint.php`

use Phpdftk\Pdf\Conformance\Profile\PdfVtProfile;

$writer->setConformance(PdfVtProfile::VT1);

Tests

PdfVtEandRIntegrationTest.php — VT-1/VT-2/VT-2s end-to-end

PDF/E — Engineering Documents

ISO 24517-1 supports 3D models, geospatial data, and interactive engineering content.

Profile enum: PdfEProfile

Profiles

Case	ISO Part	PDF
`E1`	ISO 24517-1	1.6

What gets enforced

3D content must use valid U3D or PRC streams with defined views
JavaScript and Launch actions prohibited
OutputIntent recommended (warning if missing)
All fonts embedded, no encryption
XMP metadata with identification

Constraints

Constraint	Source
Metadata	`MetadataConstraint.php`
Encryption	`EncryptionConstraint.php`
FontEmbedding	`FontEmbeddingConstraint.php`
ThreeDContent	`ThreeDContentConstraint.php`
PdfEAction	`PdfEActionConstraint.php`
PdfEColorSpace	`PdfEColorSpaceConstraint.php`

use Phpdftk\Pdf\Conformance\Profile\PdfEProfile;

$writer->setConformance(PdfEProfile::E1);

Tests

PdfVtEandRIntegrationTest.php — E-1 end-to-end

PDF/R — Raster Image Transport

ISO 23504-1 is designed for scanned document workflows where raster content is primary.

Profile enum: PdfRProfile

Profiles

Case	ISO Part	PDF
`R1`	ISO 23504-1	2.0

What gets enforced

Raster-only content expected (non-raster triggers warning)
JavaScript and Launch actions prohibited
Font presence triggers warning (raster docs shouldn’t need text fonts)
No encryption

Constraints

Constraint	Source
Metadata	`MetadataConstraint.php`
Encryption	`EncryptionConstraint.php`
RasterContent	`RasterContentConstraint.php`
PdfRAction	`PdfRActionConstraint.php`
PdfRFont	`PdfRFontConstraint.php`

use Phpdftk\Pdf\Conformance\Profile\PdfRProfile;

$writer->setConformance(PdfRProfile::R1);

Tests

PdfVtEandRIntegrationTest.php — R-1 end-to-end

Factur-X / ZUGFeRD — E-Invoicing

Built on PDF/A-3b, these profiles add structured invoice data as an embedded XML file.

Profile enum: ZugferdProfile

Profiles

Case	Description	Base Profile
`MINIMUM`	Minimum invoice data	PDF/A-3b
`BASIC_WL`	Basic without lines	PDF/A-3b
`BASIC`	Basic invoice	PDF/A-3b
`EN16931`	EU norm compliant	PDF/A-3b
`EXTENDED`	Extended data	PDF/A-3b
`XRECHNUNG`	German e-invoice	PDF/A-3b

What gets enforced

All PDF/A-3b constraints plus:

XML invoice file embedded via FileSpec/EmbeddedFile (named factur-x.xml or xrechnung.xml)
Factur-X XMP metadata with conformance level identification

Constraints

Inherits all PDF/A-3b constraints plus:

Constraint	Source
ZugferdXmp	`ZugferdXmpConstraint.php`
ZugferdInvoice	`ZugferdInvoiceConstraint.php`

use Phpdftk\Pdf\Conformance\Profile\ZugferdProfile;

$writer->setConformance(ZugferdProfile::EN16931);

Tests

ZugferdIntegrationTest.php — All profile levels

PDF/mail — Email-Safe Documents

ISO 23053-2 ensures documents can be safely attached to and opened from email without triggering security concerns.

Profile enum: PdfMailProfile

Profiles

Case	ISO Part	PDF
`Mail1`	ISO 23053-2	2.0

What gets enforced

No encryption
No JavaScript or Launch actions
No interactive forms (AcroForm)
No multimedia content
All fonts embedded
Pins to PDF 2.0

Constraints

Constraint	Source
FontEmbedding	`FontEmbeddingConstraint.php`
Encryption	`EncryptionConstraint.php`
Metadata	`MetadataConstraint.php`
Action	`ActionConstraint.php`
Form	`FormConstraint.php`
Multimedia	`MultimediaConstraint.php`

use Phpdftk\Pdf\Conformance\Profile\PdfMailProfile;

$writer->setConformance(PdfMailProfile::Mail1);

Tests

PdfMailIntegrationTest.php — mail-1 end-to-end

Constraint Matrix

Shows which constraints apply across all standard families.

Constraint	Source	A	UA	X	X-5	VT	E	R	ZUGFeRD	mail
FontEmbedding	`FontEmbeddingConstraint.php`	✓	✓	✓	✓	✓	✓		✓	✓
Encryption	`EncryptionConstraint.php`	✓		✓	✓	✓	✓	✓	✓	✓
Metadata	`MetadataConstraint.php`	✓	✓	✓	✓	✓	✓	✓	✓	✓
OutputIntent	`OutputIntentConstraint.php`	✓		✓	✓	✓			✓
ColorSpace	`ColorSpaceConstraint.php`	✓							✓
Action	`ActionConstraint.php`	✓							✓	✓
EmbeddedFile	`EmbeddedFileConstraint.php`	✓							✓
Transparency	`TransparencyConstraint.php`	A-1		X-1a/X-3					A-1
Filter	`FilterConstraint.php`	A-1
TaggedStructure	`TaggedStructureConstraint.php`	Level A	✓						Level A
DisplayDocTitle	`DisplayDocTitleConstraint.php`		✓
TabOrder	`TabOrderConstraint.php`		✓
Annotation	`AnnotationConstraint.php`		✓
TrimBox	`TrimBoxConstraint.php`			✓	✓	✓
Trapped	`TrappedConstraint.php`			✓	✓	✓
DPartRoot	`DPartRootConstraint.php`					✓
ThreeDContent	`ThreeDContentConstraint.php`						✓
PdfEAction	`PdfEActionConstraint.php`						✓
PdfEColorSpace	`PdfEColorSpaceConstraint.php`						✓
RasterContent	`RasterContentConstraint.php`							✓
PdfRAction	`PdfRActionConstraint.php`							✓
PdfRFont	`PdfRFontConstraint.php`							✓
ReferenceXObject	`ReferenceXObjectConstraint.php`				✓
ZugferdXmp	`ZugferdXmpConstraint.php`								✓
ZugferdInvoice	`ZugferdInvoiceConstraint.php`								✓
Form	`FormConstraint.php`									✓
Multimedia	`MultimediaConstraint.php`									✓