Conformance Validation

phpdftk is the only PHP PDF library with built-in conformance validation for all major PDF subset standards. Set a profile, and the library enforces every applicable constraint at generate time — no external validators needed, no post-hoc checking, no guesswork.

8 standards, 31 levels, one API call

Standard	What it guarantees	Levels
PDF/A (ISO 19005)	Documents remain readable for decades	11 levels
PDF/UA (ISO 14289)	Documents are accessible to assistive technology	2 levels
PDF/X (ISO 15930)	Colors reproduce correctly in print	6 levels
PDF/VT (ISO 16612)	Variable data prints at production speed	3 levels
PDF/E (ISO 24517)	Engineering drawings with 3D content	1 level
PDF/R (ISO 23504)	Scanned documents transport reliably	1 level
Factur-X (ZUGFeRD)	Invoices are machine-readable across the EU	6 levels
PDF/mail (ISO 23053)	Documents open safely from email	1 level

Every level is validated by veraPDF and Matterhorn Protocol in CI. See About the Suites for what we test, or the Latest Compliance Report for current results.

Usage

One line to enable

use Phpdftk\Pdf\Writer\PdfWriter;
use Phpdftk\Pdf\Conformance\Profile\PdfAProfile;

$writer = new PdfWriter();
$writer->setConformance(PdfAProfile::A2b);

// Build your document normally...
$page = $writer->addPage(612, 792);
$font = $writer->addFont(new TrueTypeFont(/* ... */));

$writer->save('archive.pdf');
// Done. The output is guaranteed PDF/A-2b compliant.

The library handles everything automatically:

• Injects XMP identification metadata (pdfaid:part, pdfaid:conformance)
• Pins the PDF version to the profile’s requirement
• Validates all constraints before emitting a single byte
• Throws ConformanceException if any rule is violated

Dual compliance

Combine profiles for documents that must meet multiple standards — accessible archival documents, for example:

use Phpdftk\Pdf\Conformance\Profile\PdfAProfile;
use Phpdftk\Pdf\Conformance\Profile\PdfUaProfile;

$writer->setConformanceProfiles([PdfAProfile::A2a, PdfUaProfile::UA1]);
// Output satisfies BOTH PDF/A-2a and PDF/UA-1 simultaneously.

Early validation

Check conformance before generating the full PDF:

$results = $writer->checkConformance();
foreach ($results as $result) {
    if (!$result->isCompliant) {
        foreach ($result->violations as $violation) {
            echo "{$violation->severity->value}: {$violation->message}\n";
        }
    }
}

Lenient mode

Collect violations without throwing — useful for migration or auditing:

$writer->setConformance(PdfAProfile::A1b, strict: false);
$writer->save('output.pdf');

$results = $writer->getConformanceResults();
// Inspect violations without blocking output

What gets enforced

27 constraint rules across all standards, each enforcing specific ISO clauses:

Constraint	What it catches
Font embedding	Missing font programs — text won’t render on other systems
Color space	Device-dependent colors that print differently everywhere
Metadata	Missing XMP identification — validators won’t recognize the profile
Transparency	Blend modes that older RIPs can’t handle
Encryption	Password protection that prevents archival access
Actions	JavaScript/Launch that pose security or reproducibility risks
Tagged structure	Missing accessibility tree — screen readers can’t navigate
Output intent	No color management — unpredictable print reproduction
Annotations	Missing alt text — inaccessible to assistive technology
Tab order	Wrong reading order for keyboard navigation
Trim box	Print production can’t determine final page dimensions
Embedded files	Prohibited attachments that break archival guarantees

Plus specialized constraints: DPartRoot for variable data, 3D content validation for engineering, raster-only enforcement, invoice XML presence, and multimedia prohibition.

See ISO Standards for the full per-standard breakdown.

Validate existing PDFs

Not just for PDFs you generate — validate any PDF against any profile:

use Phpdftk\Pdf\Conformance\ConformanceChecker;
use Phpdftk\Pdf\Conformance\Profile\PdfAProfile;

$checker = ConformanceChecker::open('existing.pdf');
$results = $checker->checkProfile(PdfAProfile::A1b);

// Or check multiple profiles
$results = $checker->checkProfiles([PdfAProfile::A1b, PdfUaProfile::UA1]);

Same constraint engine, same rules — regardless of which tool generated the PDF.

Installation

composer require phpdftk/pdf-conformance

Add alongside the writer:

composer require phpdftk/pdf-writer phpdftk/pdf-conformance