PDF/A and PDF/UA capabilities

Fork PDF can generate archival PDF/A and tagged PDF/UA output, either standalone or in supported combinations. Font embedding is verified independently. PDF/A status is stable; PDF/UA status remains experimental until the human screen-reader audit.

Capability status

Capability	Status	Notes
Font embedding verification	Stable	Every used font must be embedded and Unicode-mapped.
Strict font policy	Stable	Rejects external stylesheets, non-inline fonts, and system fallback.
PDF/A-2b / 2u / 2a	Stable	PDF 1.7, machine-validated with veraPDF.
PDF/A-3b / 3u / 3a	Stable	PDF 1.7, machine-validated with veraPDF.
PDF/A-4	Stable	PDF 2.0, machine-validated with veraPDF.
PDF/UA-1	Experimental	Machine-validated; human screen-reader audit pending.
PDF/UA-2	Experimental	Machine-validated; human screen-reader audit pending.

Compatibility matrix

Request	Result
`pdfA: "2b" \| "2u" \| "2a"`	Standalone PDF/A-2, PDF 1.7.
`pdfA: "3b" \| "3u" \| "3a"`	Standalone PDF/A-3, PDF 1.7.
`pdfA: "4"`	Standalone PDF/A-4, PDF 2.0.
`pdfUa: 1`	Standalone PDF/UA-1, PDF 1.7.
`pdfUa: 2`	Standalone PDF/UA-2, PDF 2.0.
`pdfUa: 1` + PDF/A-2/3	Combined PDF 1.7 output.
`pdfUa: 2` + `pdfA: "4"`	Combined PDF 2.0 output.
`pdfUa: 1` + `pdfA: "4"`	Rejected with `UNSUPPORTED_COMPLIANCE_COMBINATION`.
`pdfUa: 2` + PDF/A-2/3	Rejected with `UNSUPPORTED_COMPLIANCE_COMBINATION`.

Standalone PDF/A

{
  "htmlContent": "<h1>Archived report</h1>",
  "compliance": { "pdfA": "3b" }
}

The response omits x-pdf-ua and pdfUa from complianceStatus.

Combined PDF/A + PDF/UA

{
  "htmlContent": "<h1>Accessible archive</h1>",
  "compliance": { "pdfUa": 1, "pdfA": "3b" },
  "fontPolicy": "strict"
}

Response status

{
  "compliance": { "pdfUa": 1, "pdfA": "3b" },
  "complianceStatus": {
    "fontPolicy": "strict",
    "fontEmbedding": "verified",
    "pdfA": "stable",
    "pdfAFlavor": "3b",
    "pdfUa": "experimental",
    "pdfUaVersion": 1
  }
}

JSON, webhook, and stream-only responses use the same status object. Stream-only clients read it from x-compliance-status (base64 JSON).

Response headers

x-pdf-a: 3b
x-pdf-ua: 1
x-font-embedding: verified
x-font-policy: strict
x-compliance-status: <base64 JSON>

Font policy

fontPolicy: "warn" is the default. It reports advisory warnings. fontPolicy: "strict" rejects external stylesheets, non-inline @font-face rules, and system/generic font fallback with FONT_POLICY_STRICT.

Capability discovery

curl https://api.forkpdf.com/v1/compliance/capabilities

The response lists supported PDF/A flavors, PDF/UA versions, valid combinations, font policies, and the current forms limitation.

Errors

Code	HTTP	Meaning
`EMPTY_COMPLIANCE`	400	No `pdfUa` or `pdfA` was provided.
`UNSUPPORTED_COMPLIANCE_STANDARD`	400	Unsupported PDF/A version.
`UNSUPPORTED_COMPLIANCE_COMBINATION`	400	The PDF/UA and PDF/A versions cannot be combined.
`UNSUPPORTED_PDF_UA_VERSION`	400	Only PDF/UA-1 and PDF/UA-2 are supported.
`COMPLIANCE_FORM_UNSUPPORTED`	400	Compliance cannot be combined with `pdfForm` yet.
`FONT_POLICY_STRICT`	422	Strict font policy rejected the source.

Limitations

Only one PDF/A flavor and one PDF/UA version can be claimed per document.
PDF/A-2/3 require PDF 1.7; PDF/A-4 requires PDF 2.0.
PDF/UA-1/2 remain experimental until the human screen-reader audit.
Compliance and pdfForm cannot be combined until tagged form fields are implemented.
PDF/A does not imply PDF/UA, and PDF/UA does not imply PDF/A.