I wanted a complete PDF editor running entirely in the browser — page reordering, annotations, highlights, a drawn signature, watermark — on the same zero-upload principle as the rest of my site's tools. The interesting technical problem wasn't the interface. It was redaction.
A black box drawn over text in a PDF covers it visually, but the text stays in the document underneath, selectable and copyable. I wanted to fix that properly.
The naive approach (and why it's wrong)
Most "redact PDF" tools out there just draw a shape over the text:
// ❌ Just draws a black rectangle over existing content
