I built this as an experiment after realizing that “editing PDFs” is fundamentally broken. Instead of modifying PDF internals, DCP treats PDFs as immutable surfaces and applies deterministic visual deltas (whiteout + overlay) on top. The original PDF is never modified. All edits live in a JSON delta ledger. Think: Git for 2D surfaces.

Hi HN! I built DCP after struggling with PDF corruption in a document workflow.

Instead of editing PDF internals (which breaks things), DCP treats the PDF as an immutable substrate and applies JSON-defined visual deltas on top.

Think of it as "Git for document surfaces" – you get: - Deterministic rendering (same input = same pixels) - Full audit trail (delta.json is human-readable) - Zero risk of corrupting the original

Would love feedback on the protocol design (SPEC.md).

Editing PDFs is not broken.

Just because you don't understand something complex, does not mean it is broken.