This tool merges PDF files free online, combining multiple PDFs into a single file in whatever order you choose. Add two or more PDFs, reorder them with the up/down arrows if needed, then merge — the combined file downloads straight from your browser. Unlike the other tools on this site, merging never touches a server: your files are read and combined entirely on your own device using pdf-lib, a JavaScript PDF library, so nothing is ever uploaded anywhere. That also means there's no file-size limit tied to server cost — the only real limit is your own browser's available memory, so this tool can comfortably handle much larger files than the 25MB cap on our server-side tools.