pdfcosmos

Merge PDF

Combine several PDFs into a single file, in the exact order you choose.

Free, fast, and privacy-first.

Combine your PDF files

or drag & drop files here

PDF files onlyup to 100 MB each300 MB total

Merge PDF files online, free and completely private

Combining PDFs shouldn't mean uploading sensitive documents to someone else's server. pdfcosmos merges your files entirely inside your browser with WebAssembly, so a contract, a scanned ID, or a bank statement never leaves your device. There's no upload wait, no account, and no watermark added to the result.

Add as many PDFs as you need, drag them into the exact order you want, and rotate any file that arrived sideways before you combine them. If you only need part of a file, set its card to a custom page range (like 1-3, 5); you can also sort the queue by file name and name the finished PDF. Because every step runs locally, large files merge as fast as your device can read them, and you can keep working even after you go offline.

  • Nothing leaves your device

    Files are processed in the browser and never sent anywhere. Open your Network tab and watch while you merge.

  • Merge in the order you choose

    Reorder the file cards by dragging (or with the arrow buttons) and rotate any file 90° at a time before combining.

  • Free, with no watermark

    No sign-up, no install, and nothing stamped onto your finished PDF. Every tool is completely free.

  • Your quality stays intact

    Pages are copied as-is, so text remains selectable and images keep their original resolution.

How to merge PDF files

  1. Add your PDFs

    Click “Add PDFs”, or drag your files into the upload area. Add as many as you need.

  2. Arrange and select

    Drag the file cards (or use the arrow buttons) to order them, rotate any file, and optionally set a card to a custom page range to include only some of its pages.

  3. Merge and download

    Click “Merge PDF” to combine everything into one file, then download it, all in your browser.

Frequently asked questions

Are my PDF files uploaded to a server?
No. Files are processed entirely in your browser using WebAssembly. They never leave your device. You can confirm it by opening your browser's Network tab while merging: no file data is sent.
Is there a limit on file size or number of files?
There's no fixed limit on how many PDFs you can merge. For speed and reliability across devices, each file should be under 100 MB and the total under 300 MB. Larger files are skipped with a clear message.
Can I choose the order of the merged pages?
Yes. Drag the file cards to reorder them (or use the up/down buttons on each card). The PDFs are merged in the exact order shown, top to bottom. You can also use the “Sort files” menu to reorder the whole queue by name (A–Z or Z–A), or restore the original added order — handy for scanned files like scan_001.pdf.
Can I merge only some pages from a file?
Yes. On any file's card, choose “Custom range” and enter the pages to include — for example “1-3, 5”. Cards default to All pages. The range box only accepts page numbers, commas and hyphens, and each range is checked against that file's page count, so an out-of-range entry is flagged before you merge.
Can I name the merged file?
Yes. Set “Output file name” in the settings and your merged PDF downloads with that name. Leave it blank to use merged.pdf.
Can I add a blank page between the merged PDFs?
Yes. Turn on “Add a blank page between files” in the settings and one empty page is inserted in each gap between your PDFs — handy for separating documents or making each one start on a fresh sheet when printing double-sided. You can match the blank to the previous page's size, or set a fixed A4, US Letter, or US Legal size.
Can I rotate a PDF before merging?
Yes. Each file card has a rotate button (↻) that turns that PDF 90° clockwise. Tap again for 180° or 270°. The rotation is applied as the files are combined, so each one goes into the merged PDF facing the way you set it.
Do I need an account or to install anything?
No. There's no sign-up and nothing to install. The tool runs entirely in your browser.
What happens to my files after I merge them?
Nothing is stored. Your files stay in memory only while the tab is open. Clicking “Reset queue” or closing the tab clears everything immediately.
Will merging reduce the quality of my PDFs?
No. Each page is copied into the combined file exactly as-is. pdfcosmos never re-compresses or rasterizes your pages, so text stays sharp and selectable and images keep their original resolution.
Can I merge password-protected PDFs?
Unlock them first with our Unlock PDF tool (also entirely in your browser), then add the unlocked files here. A still-encrypted PDF can't be merged without its password.
Can I merge PDFs on my phone?
Yes. The tool is fully responsive and touch-friendly, so you can add files, drag to reorder them, and download the merged PDF from any modern mobile browser, with the same in-browser privacy.
Is Merge PDF free?
Yes, it's completely free to use.