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Merge PDFs without uploading them: what people actually want

People who look for another PDF tool rarely want anything new. They want the same handful of jobs they do every week: put three scans into one file, pull two pages out of a long report, shrink an attachment so the email goes through, make a scanned letter searchable, sign a contract. What changes is the conditions they want those jobs done under.

Three conditions come up again and again:

• No size or file caps. A 300-page scanned contract or a folder of 40 invoices should not need splitting into batches first.
• No daily quota and no account. Merging two files on a Tuesday afternoon should not depend on how many you merged in the morning, or on remembering a password.
• No uploading. This is the one that matters most. A payslip, a tenancy agreement, a medical report or a client file contains names, addresses, bank details and ID numbers. Sending it to a website means trusting a server you know nothing about, for a task your own computer can do in seconds.

If you are weighing up any online service against a desktop app, read its terms and its privacy policy and decide for yourself; conditions change, so check them each time rather than relying on what a friend told you. This article does not compare services. It explains what to look for when you want to merge PDFs without uploading them, and how Airpic PDF does each job on your own machine.

A quick test that works for any tool: switch off your Wi-Fi and try the job. If it still works, the file never left your computer. If it stalls, it was going somewhere. Airpic PDF passes that test for all fourteen functions, because none of them needs a network connection.

A free PDF editor for your computer: what Airpic PDF does

Airpic PDF is a free desktop application for macOS 12 or later and Windows 10 and 11 (64-bit). You download it once, and from then on everything happens locally: no account, no sign-in screen, no size limit beyond your computer's memory, and no document ever leaves the machine. It is the PDF side of Airpic, the same team behind the image and video tools on this site, and it was previously called PDFeitor.

It covers fourteen functions, each with its own page explaining the steps:

• Merge PDF files into one document, in the order you choose.
• Split a PDF into separate files or extract a page range.
• Reorder, rotate and delete PDF pages by dragging thumbnails.
• Compress a PDF so it fits under an email attachment limit.
• OCR a PDF: add a searchable, copyable text layer to a scan (Apple Vision on Mac, PP-OCR on Windows).
• Sign a PDF with a handwritten signature, which you can also draw on your phone via a QR code.
• Digitally sign a PDF with a certificate (.p12 or .pfx).
• Convert PDF to Word.
• Convert JPG to PDF, including PNG and HEIC photos from a phone.
• Convert PDF to JPG or other images.
• Password-protect a PDF.
• Add a watermark to a PDF.
• Add page numbers to a PDF.
• Fill in a PDF form.

One thing to know before you download: the app's interface is in Spanish for now. The buttons are short and the guides on each page give the Spanish label with its English meaning, for example «Abrir» (Open), «Unir» (Merge) and «Eliminar» (Delete), so you can follow along without speaking the language. We would rather tell you that here than have you discover it after installing.

For quick jobs there is also a lighter option. Merge, split and compress work directly in your browser on their pages: the file is processed by JavaScript on your device and is never sent to a server. The desktop app is the better choice for big files, for scans that need OCR, and for anything with forms or signatures, because the browser version does not preserve fillable fields or digital signatures when merging or splitting.

When it matters that your PDFs stay on your computer

For a takeaway menu or a public brochure, it hardly matters where the file is processed. For a lot of everyday paperwork it does, and those are exactly the documents people merge, compress and sign most often:

• Contracts and leases. Signed copies carry names, addresses, signatures and sometimes passport numbers.
• Payslips and tax documents. Salary, National Insurance or tax reference numbers, bank account details. Mortgage brokers and letting agents routinely ask for three months of payslips merged into one PDF, which is precisely the job where people reach for the first website that turns up.
• Medical records. Test results, referral letters, insurance claims. Health data is a special category under the GDPR, and the safest copy is the one you never sent.
• Client files. Accountants, lawyers, HR staff and clinics handle other people's data. Many company policies forbid uploading it to any third-party service that has not been approved, and a free website almost never has been.

Processing locally removes a whole category of questions. There is no server copy to ask about, no retention period to look up, no country to check. The data protection question becomes the same one you already answer for every other file on your laptop: who has access to this computer.

That is also the honest limit of the argument. Local processing protects the document from the trip, not from everything. If your laptop is shared, unencrypted or full of malware, a desktop app does not fix that. Turn on FileVault on a Mac or BitLocker on Windows, lock the screen, and store the merged file somewhere sensible. And if you then email the merged contract to five people, it has left your computer anyway; Airpic PDF can at least add a password to it first.

Airpic follows the same principle on the image side, even though those tools need a GPU and so do run on a server: files are deleted one hour after download and within one day at most, they are never used for training, and the GPUs are in the European Union. If you photograph documents with your phone rather than scanning them, you can compress images before turning them into a PDF; that tool is free, including the download.

Installing it, and why macOS and Windows show a warning

The first time you open Airpic PDF, your operating system will warn you. This is expected, and it is worth understanding why rather than just clicking past it.

macOS and Windows trust installers that carry a developer signature: a certificate from Apple, or from a code-signing authority for Windows, that ties the file to a verified publisher. Airpic PDF's installers are not signed with one yet. The app is the same either way; the warning only means the system cannot confirm who published it. We say this up front on the download page as well.

On a Mac:

1. Open the .dmg file and drag Airpic PDF into the Applications folder.
2. Open it. macOS says it cannot verify the developer. Close that message.
3. Go to System Settings, then Privacy & Security, scroll down to the notice about Airpic PDF and click “Open Anyway”. You only do this once.
4. From then on it opens with a double click, and you can use “Open With” on any PDF in Finder.

There are separate downloads for Apple silicon (M1 and later) and Intel Macs; the download page picks the likely one and links to the other.

On Windows:

1. Run the installer. It does not need administrator rights.
2. If SmartScreen shows “Windows protected your PC”, click “More info” and then “Run anyway”.
3. If Microsoft Edge WebView2 is missing (it ships with Windows 11), the installer downloads it for you.

Two pieces of advice that run against what you may read in forums. First, do not switch off Gatekeeper or SmartScreen to get rid of the message. You only need an exception for this one file; turning the protection off for everything is a bad trade. Second, if you want proof that the installer is the one we published, check its SHA-256 fingerprint: the download page lists it together with the exact command for Terminal (Mac) or PowerShell (Windows). A matching hash shows the file has not been altered on the way; it does not replace a developer signature.

And the case where none of this helps: on a work computer, IT policy may block unsigned installers outright. Do not try to get round it. Ask your administrator, or use the browser version of merge, split and compress, which needs no installation and still keeps the file on your device.

Free software to merge PDF files: step by step in Airpic PDF

Merging is the job most people come for, so here it is in full. The button labels are given in Spanish, as they appear in the app, with the English meaning.

1. Open the first PDF. Click «Abrir» (Open) or simply drag the file onto the window. Its pages appear as thumbnails. Start with whichever document should come first; it saves reordering later.
2. Add the next file. Click «Unir» (Merge) and pick the second PDF. Its pages are appended at the end of the current document. Repeat for as many files as you need; there is no cap on the number of files or their size, only your computer's memory.
3. Check the order. Drag thumbnails to rearrange pages. For three months of payslips, this is where you put August before September if the files were named badly.
4. Remove what you do not need. Select a page and click «Eliminar» (Delete). This is also how you merge only part of a document: add the whole file, then delete the pages you do not want.
5. Save. Press ⌘S on a Mac or Ctrl+S on Windows. Pages are copied as they are, so text stays selectable, links keep working and images keep their original quality.

If the merged file is too heavy to email, the next step is to compress the PDF. Compression works on the images inside the file, which is where the weight is: in our own test of the in-browser version, a scanned PDF went from 253 KB to 87 KB, while a text-only PDF of 51 KB only dropped to 47 KB. So do not expect much from a document that is mostly typed text; it is already small.

If the merged pages are scans you will need to search later, run OCR on the PDF before you file it. If it is a contract going out for signature, sign the PDF in the same window, and add a password to the PDF before attaching it to an email.

For a quick merge you need right now, without installing anything, the merge PDF without uploading page has a merger that runs in your browser: drop the files, use the arrows to set the order, and download. For everything else, the free PDF editor for Mac and Windows page has the download links and the full list of functions.

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