Nothing is uploaded. When you drop or pick your PDFs, the tool reads each one locally with the browser’s File API, renders a first-page thumbnail with the pdf.js engine (whose worker is bundled locally, not fetched from a CDN), and merges the pages with the pdf-lib library inside a Web Worker on your own machine. There is no server, upload, database, API or tracking anywhere in the processing path, so contracts, statements, scans and private paperwork stay on your device; the tool works offline once cached, and closing the tab discards everything. The only optional network use anywhere on the site is consent-gated advertising, which never sees your files.

After you add your PDFs, each one becomes a card showing its first-page thumbnail, file name, size and page count, with a numbered badge marking its place in the sequence. Grab any card and drag it to a new position — the badges renumber instantly — so you can arrange, for example, a cover page first and appendices last. You can also click “Add more files” to append extra PDFs, or remove any file with its close button. When the order looks right, click Merge and the pages are combined from the top card down, giving you a single document that follows the sequence you set.

Merging requires a minimum of two PDFs (the button stays disabled until you have added a second file). Beyond that there is no hard cap on how many documents or pages you combine, and the tool shows a running total of files, pages and size as you build the list. Because the entire merge happens in browser memory rather than on a server, the real limit is the RAM available to your browser tab: a handful of ordinary documents merges in a moment, while dozens of large, image-heavy scans use more memory and take a little longer. If a device is very constrained, merge in smaller batches and then combine the results.

The merge does not re-encode or re-render your pages, so there is no quality loss — pdf-lib copies each source page’s content, fonts, images and vector graphics verbatim into a new document, which means text remains selectable and searchable and the layout is identical to the originals. One honest caveat: because pages are copied individually, document-level extras such as the outline (bookmarks) and some interactive form-field states may not carry across, and named-destination links between files can shift; if a merged form or table of contents matters, check it afterwards. For the page content itself, what you put in is exactly what you get out.