PDF Studio is a PDF editor that works entirely in the browser: no files are uploaded to a server; all processing remains on the user's device. This is the project's central architectural choice, solving the typical privacy issue of online PDF editors. It allows you to add text, images, shapes, and annotations, and manage pages by reordering, rotating, deleting, duplicating, merging, and splitting documents. Technically, it relies on pdf.js for rendering and pdf-lib for all editing and export operations.