Node.js Document Previews — Signed Watermark Evidence Beyond the First PDF Page

Generate the first-page thumbnail only after the external-share watermark has been applied, then bind that thumbnail to the exact output PDF with a content digest and a signed audit record. The deciding constraint is evidentiary: a fast image that cannot be traced to the bytes a recipient received is decoration, not proof. TL;DR: Put PDF validation, watermarking, first-page rasterization, and…