oc-pdf-filler 0.1.4

Extract and fill PDF AcroForm fields with a multi-backend fallback chain (pypdf, pdfrw, PyMuPDF, pdftk).

oc-pdf-filler

Extract and fill PDF AcroForm fields from the command line, with a multi-backend fallback chain so a single quirky PDF doesn't block your workflow.

The repo ships two artifacts:

1. A Python package and CLI: oc-pdf-filler (subcommands: extract, fill, list-backends).
2. An OpenClaw / AgentSkills skill at skills/pdf-filler/ that wraps the CLI so agents can use it.

Why a fallback chain?

PDF AcroForms are notoriously inconsistent. The orchestrator tries each backend in order and stops at the first one that fills every requested field:

1. pypdf -- pure Python, required dependency.
2. pdfrw -- fine-grained dictionary control (optional).
3. PyMuPDF -- robust appearance regeneration, native checkbox/radio handling (optional).
4. pdftk -- system binary, last resort (optional).

Backends without their dependency present are skipped automatically.

Install

pip install -e ".[all]"          # full fallback chain (pypdf + pdfrw + PyMuPDF)
# or, minimal:
pip install -e .                 # pypdf only
# Optional system dep:
brew install pdftk-java          # macOS
apt install pdftk-java           # Debian/Ubuntu

Verify your backends:

oc-pdf-filler list-backends

CLI usage

Extract a field schema

oc-pdf-filler extract form.pdf --output schema.json --include-values

Output is JSON with one entry per field:

{
  "field_count": 27,
  "fields": [
    {
      "name": "Name Verantwortlicher",
      "type": "text",
      "value": "ACME GmbH",
      "options": [],
      "max_length": null,
      "required": false,
      "multiline": false,
      "read_only": false
    }
  ]
}

type is one of text, checkbox, radio, choice, signature, pushbutton, unknown.

Fill a PDF

Build a JSON values file. Field names come from the schema verbatim.

{
  "Name Verantwortlicher": "ACME GmbH",
  "Postleitzahl Verantwortlicher": "10115",
  "Beschäftigte": true,
  "Verarbeitungstyp": "Automatisiert"
}

Then run:

# default: writes ./form_done.pdf next to your cwd
oc-pdf-filler fill form.pdf values.json
# or pass --output explicitly
oc-pdf-filler fill form.pdf values.json --output filled.pdf

Useful flags:

Flag	Effect
--backend NAME	Force one of pypdf / pdfrw / pymupdf / pdftk (default: auto)
--best-effort	Chain backends so partial fills accumulate
--flatten	Bake values into the PDF (best support: PyMuPDF, pdftk)
--strict	Exit non-zero if any field is missing or unfillable

Value coercion per field type

Type	JSON value
text	string (newlines preserved when multiline is true)
checkbox	true / false or "true", "yes", "on", "x", "1", "checked"
radio	string equal to one of the entries in the field's options array
choice	string equal to one of the dropdown options
signature	not supported -- reported in the schema, ignored at fill time

Tests

pip install -e ".[dev]"
pytest -q

Tests run against the three real PDFs in test_pdfs/ and parametrize across every available backend. They round-trip text and checkbox values (fill, re-extract, assert).

OpenClaw skill

The skills/pdf-filler/ folder is an AgentSkills.io spec-compliant skill that an OpenClaw agent can load to get PDF-filling capabilities. It contains:

skills/pdf-filler/
├── SKILL.md                    # frontmatter + instructions
├── scripts/
│   ├── extract.py
│   ├── fill.py
│   └── list_backends.py
├── references/
│   ├── FIELD_TYPES.md
│   └── BACKENDS.md
└── assets/
    └── values.example.json

Validate it:

npx skills-ref validate ./skills/pdf-filler

Releasing a new version

Bump metadata.version in skills/pdf-filler/SKILL.md, then run:

clawhub publish ./skills/pdf-filler --version <semver>

--version is required and must be valid semver, and should match metadata.version so the registry record stays in sync.

The agent that loads the skill needs oc-pdf-filler installed in its workspace Python environment for the scripts to run; the skill's compatibility field documents this.

License

MIT