About PaperKit

What it is

PaperKit is a set of PDF and image tools that run entirely in your browser. You can merge, split, compress, crop, rotate, number, watermark, sign, protect, unlock, scan, OCR and repair PDFs, and convert, compress and clean up photos, without creating an account and without your files leaving your device.

It started as a toolkit for academic papers (margins, page numbers, page sizes for journal submissions) and grew into a general PDF workbench. The academic guides are still here.

How it works

When you open a tool, your browser downloads the page and the code for that tool. From then on the work happens on your machine. PDFs are read and written with pdf-lib, pages are rendered with pdf.js (the engine inside Firefox), images go through the browser canvas, encryption uses WebCrypto, HEIC photos are decoded with libheif compiled to WebAssembly, and text recognition uses Tesseract compiled to WebAssembly.

There is no upload step because there is no server that could receive a file. The site is a folder of static files. That is also why there are no file size limits beyond your device memory, and why the tools keep working if your connection drops after the page has loaded.

What it does not do

Some jobs need a server-grade engine: converting PDFs to editable Word or Excel files with faithful layout, for example. PaperKit does not offer those rather than doing them badly. Each tool page says plainly what the tool cannot do, such as fonts that cannot be shrunk, image types that are left untouched, or scans that have no text layer.

Who makes it

PaperKit is built and maintained by an independent developer. It is free because it costs almost nothing to run: the computing happens on your device, and hosting static files is cheap.