# `POST /v1/kyb/cases/{id}/documents` — Upload a commercial register extract

multipart/form-data with field "file" (PDF, JPEG or PNG, at most 10 MB) and optional "kind" (register_extract or other). Stored encrypted for your reviewers. Needs kyb:write.

Parameters:
- `id` (path, string, required)

Responses:
- 201: Stored: id, kind, size, sha256.
- 413: Larger than 10 MB.
- 422: Not a PDF, JPEG or PNG.