Merge PDF Files

Scanned contracts, signed forms, invoice batches, chapters of a report — sooner or later almost everyone ends up with several PDF files that really belong together as one document. Mailing five separate attachments or asking a client to open five links instead of one is clumsy, and most free online "PDF merger" sites solve this by quietly uploading your files to a server first, which is exactly the kind of trust few people want to extend to a document that might contain a signature, an ID number, or financial details.

This tool never does that. Everything runs inside your browser using pdf-lib, a JavaScript library that reads the raw structure of each PDF, copies its pages into a new document, and reassembles the result — all in memory, on your device. Page thumbnails are rendered locally too, with pdf.js (the same rendering engine built into Firefox), so you can see exactly what you're working with before anything is combined.

Add your PDF files by clicking the button or dragging them into the drop zone — every page from every file appears as its own thumbnail, in one combined grid, not grouped by file. Drag any thumbnail to reorder it relative to all the others, even across different source files, or use the arrow buttons if dragging isn't convenient. Click a page's rotate button to turn it 90° at a time, or its delete button to leave it out of the final document entirely — useful for dropping a blank scanned cover sheet or a duplicate page. Once everything looks right, press Merge PDFs; the combined file is built entirely in memory and downloads as merged.pdf.

There's no page limit built into the tool, though very large batches of scanned, image-heavy PDFs will naturally take longer to render thumbnails for since everything is processed by your own device rather than a server farm. If one file fails to load — for instance because it's encrypted with a password or got corrupted during download — this tool tells you rather than silently producing a broken result. To go the other direction and split a merged PDF back into smaller pieces, the Split PDF tool works the same privacy-first way and shares the same rotate-and-delete page controls.