JhuoW/PDF-Editor ? reverse-engineered prompt

Build me a free, lightweight PDF editor that works entirely in the browser and keeps everything local on my computer.

I want to be able to open a PDF, flip through pages easily, zoom in and out, and use a sidebar with thumbnails so I can jump around fast. Let me annotate the file with highlights, underlines, freehand drawing, shapes, and sticky notes, and also insert images where I need them. It should let me merge multiple PDFs into one file and split or extract pages too. Make the interface simple and clean, with basic save and download options, and make sure it feels fast even for bigger documents.

This needs to be private, offline friendly, and open source style, with no cloud uploads or subscription stuff. If you need to look up current docs or best practices for PDF handling in the browser, go ahead and do that.