Building a PDF processing tool that runs entirely in the browser presented unique technical challenges. Here is how we solved them. The core of our engine is PDFium, the same PDF rendering library used by Chromium, compiled to WebAssembly. This gives us access to a battle-tested PDF processing pipeline that runs at near-native speed in any modern browser.
On top of PDFium, we built a JavaScript layer that handles document manipulation — merging, splitting, page extraction, and content compression. The pdf-lib library provides the PDF document model, allowing us to read, modify, and write PDF files without any server-side dependencies.
One of the biggest challenges was memory management. Large PDFs can consume hundreds of megabytes when loaded into memory. We implemented streaming reads and incremental garbage collection to keep memory usage predictable, even for documents with hundreds of pages.
The result is a PDF processing engine that delivers desktop-class performance entirely within the browser sandbox. No plugins, no server calls, no data leaks — just fast, private document processing that works anywhere JavaScript runs.