Building browser-only PDF tools — merge, split, and canvas builder without touching a server

Most PDF processing tools have a fundamental architecture problem: they upload your files to a server to do the work. This makes sense historically — PDF manipulation used to require server-side processing. But modern browser APIs have made that unnecessary for the majority of document workflows. pdf-lib, pdfjs-dist, and Fabric.js give you everything you need to merge, split, and build PDFs entirely client-side. Here's how I built three PDF tools without a single file upload. The core libraries pdf-lib — JavaScript PDF creation and modification, runs in browser and Node. Handles merging, splitting, page manipulation, metadata. The API is clean: const { PDFDocument } = await import ( " pdf-lib " ); // Merge const merged = await PDFDocument . create (); for ( const file of files ) { const src = await PDFDocument . load ( file . bytes ); const indices = parseRanges ( file . ranges , src . getPageCount ()); const copied = await merged . copyPages ( src , indices ); copied . forEach ( page