pdf24 merge PDF: combine PDF files into one, free and private

Yes. pdf24 merge PDF costs nothing, needs no account and adds no watermark. There is no daily limit and no cap on the number of files, because the work is done by your own device rather than a paid server. The only practical limit is memory: a phone may struggle with several hundred megabytes of scans at once, which a computer handles easily.

At least 2, and as many as your device can hold in memory. In our tests 3 small files, 2 large scans and mixed sets all merged in under 1 second on a desktop. For very large sets on a phone, merge in batches of about ten files, then merge the batches, which keeps memory use low.

No. With pdf24 merge PDF the files are read by the browser from your disk and joined in the same tab with JavaScript. Nothing is sent to a server, nothing is stored, and the result line says 0 bytes uploaded after each merge. You can check it yourself: load the page, turn off the network, and the merge still works.

Yes. Every file in the list has ↑ and ↓ buttons; the merged document follows the list from top to bottom. Remove a file with ×. To change the order of single pages rather than whole files, merge first and open the result in the Rearrange PDF pages tool, where each page has its own arrows.

No. Pages are copied with their original images, fonts and vector content; nothing is re-compressed or turned into a picture. Our merged scan kept the same byte size as the source pages, which shows the images were not touched. Typed text also stays selectable and searchable in the result.

A merged PDF weighs roughly the sum of its parts, because pages are copied without re-compression. Two files of 5.1 KB and 8.07 MB gave 8.07 MB. If you need it smaller, run Compress PDF on the merged file; it can aim at an exact size such as 1 MB or 200 KB for upload forms.

This page accepts PDF files only, so pictures are skipped with a message. Use Assemble PDF instead: it takes PDFs and images in one list, turns each picture into an A4 page with a 20-point margin, and keeps the order you set. Both tools work on your device in the same way.

Links and comments placed on the pages are kept, because they belong to the page. The bookmark outline of each source file is not carried over, since it belongs to the whole document. After merging you can rebuild the outline in a minute with Bookmark PDF, which suggests one entry per page from its first line.

Yes. It works in Safari on iPhone and iPad with iOS 15 or later, without an app. Pick the files from the Files app, sort them with the arrows, merge, and find merged.pdf in Downloads. From there, Share sends it by Mail, WhatsApp or AirDrop like any other document on the phone.

Not directly. An encrypted file stops the merge with a message asking you to remove the password. Open it with Unlock PDF using the password you already know, merge the unlocked copy, and lock the merged result again if it must stay protected. The tool never tries to break a password you do not have.

Once the page has loaded, yes. The merge engine is a JavaScript library that the page downloads with the tool; after that the work needs no network at all. On a train or a plane, open the page while you still have a connection, and merging keeps working when the signal drops.

Yes. Each page keeps its own size and orientation, so an A4 letter, a Letter-size form and a landscape table can sit in one file. PDF readers simply show each page at its size. If you want every page the same size for printing, run Change PDF page size on the merged file afterwards.

No tool can keep it valid. A certificate signature protects the exact bytes of the signed file, and a merged file is a different file. The signature picture may still be visible on the page, but a reader will report the signature as invalid or missing. Keep signed files separate or sign again.

Usually under a second. Our desktop runs of pdf24 merge PDF took 0.1 s for 3 small files, 0.2 s for 2.47 MB and 0.9 s for 8.07 MB of scans. Time grows with the amount of data, not the page count. Phones are slower than desktops but stay in the range of a few seconds for normal documents.

The original files are never changed, so there is nothing to undo: they stay on your device as they were. To take the merged file apart again, open it in Split PDF and choose By ranges, for example 1-6, 7-10, which gives back the two parts as separate files in one ZIP.

It works in current versions of Chrome, Edge, Firefox, Safari, Opera and Samsung Internet on Windows, macOS, Linux, Android, iOS and ChromeOS. Internet Explorer is not supported. If the button does nothing, reload the page so the engine loads again, and check that the files are real PDFs.

No. pdf24tools is an independent website and is not affiliated with PDF24 or Geek Software GmbH. Our merge tool is our own code that runs in your browser. We use the name only to describe what people search for, and every result is processed on your device, never on our servers.