External binary adapter for Poppler's pdfsig tool.
This adapter validates that a PDF exposes one or more signatures and reports cryptographic-signature posture separately from certificate trust.
Summary
Functions
Validates a signed PDF at the given path using pdfsig.
Functions
Validates a signed PDF at the given path using pdfsig.
Returns {:ok, %{signatures: signatures}} on success.
Returns {:error, {:missing_executable, "pdfsig"}} if pdfsig is unavailable.
Returns {:error, {:invalid_pdf, reason}} if the file cannot be read or
contains no signatures.