A year ago, I got fed up with online PDF tools.

Every time I needed to merge a contract or compress a resume, I had to upload my file to someone else's server. As a developer, I knew exactly what that meant — my file was sitting on a cloud server I didn't control, processed by code I couldn't see, and potentially logged or cached somewhere I couldn't audit.

So I decided to build an alternative: a PDF toolkit that runs entirely in the browser . No server uploads. No registration walls. No privacy trade-offs.

This post is a recap of the technical decisions, the libraries I chose, and the traps I fell into along the way.

The Goal

I wanted something simple on the surface but technically non-trivial under the hood:

20+ PDF tools (merge, split, compress, rotate, watermark, convert, encrypt, etc.)

Pure browser-side processing — files never leave the user's device

Free and registration-free — open the page, use the tool, download the result

Fast and responsive — no upload/download round-trips

The live…