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18. Signing: space reserved

Date: 2026-09-12

Status​

Accepted

Context​

Business documents are signed, often by several parties in turn, and a signature covers byte ranges of the file: any rewrite that shifts bytes breaks it. Signing itself — PAdES, time stamps, validation data — is too large to hold up the foundations.

Decision​

We will reserve the space for signing in the writer from the start: the writer must be able to produce incremental updates and to leave an existing signature intact. PAdES follows, behind an IPdfSigner abstraction so signing can be delegated to an HSM or a qualified provider.

Consequences​

Recorded so the choice is not silently revisited.

Recorded as D17 before this project adopted Architecture Decision Records; the identifier still appears in commit messages and in CLAUDE.md.