Full desktop PDF editors are powerful but heavy — most people opening a PDF editor just want to add a line of text, fill in a blank, or annotate a document before sending it back. This tool is built for that specific job: a fast, in-browser way to place text anywhere on a page without installing anything.
Under the hood, the page you see is rendered using Mozilla's pdf.js library (the same engine that powers PDF viewing in Firefox and Chrome), so what you see is an accurate preview of your actual document. When you click to add text, that position and content is tracked and, when you save, permanently written into the PDF using pdf-lib — producing a real, flattened PDF file rather than an editable overlay.
Because this all happens locally, there's no file size limit imposed by a server, no processing queue, and no risk of your document being retained anywhere after you close the tab.