Most PDF processing tools send your file to a server. The browser makes a multipart POST request, the server runs LibreOffice or Ghostscript or a Python library, and you download the result. There's a better approach for many PDF operations: process the file entirely in the browser using PDF-lib and Web Workers. No server involved. No file transmission. Works offline once the page is loaded. This post explains how browser-side PDF compression works and when it's the right choice. The Architecture Client-side PDF processing in the browser uses three components: PDF-lib — a pure JavaScript PDF manipulation library. Reads and writes PDF structure without any native dependencies. Web Workers — moves the CPU-intensive processing off the main thread so the UI stays responsive. Canvas API — used to re-encode embedded images at reduced quality.…