How to Merge PDF Files on Windows, Mac and iPhone (Free & Local)

You have a contract, two annexes and a signature page. The portal accepts one PDF. Or you’ve scanned a stack of receipts one by one and now need a single file for your accountant.

That isn’t necessary. A browser can combine PDFs on the device itself. OpenToola reads the files from your disk, puts the pages together in memory and gives you a download. Nothing is sent to a server, and there is no account to create.

What follows is what actually works on Windows, Mac and iPhone, plus the checks that prevent the usual mess: pages out of order, a landscape sheet in the middle of a portrait report, or a file too large for the recipient’s inbox.

What “local” means in practice

When you choose a PDF in the browser, the file is read from your disk. The merge happens in memory, and the browser builds a new PDF for download. Your original files are not modified.

There are limits. Very large files can exhaust memory, especially on a phone. Password-protected PDFs have to be unlocked before they can be read. A corrupted file may fail without a clear error.

The upside is that you don’t hand a contract to an unknown server, and you don’t wait for a 50 MB upload on hotel Wi-Fi.

Windows: no installation needed

Open the Merge PDF tool in Edge, Chrome or Firefox. Click Select PDF files, then choose the documents in File Explorer. The order you select them is not necessarily the order they will appear, so drag the cards or use the arrows until the first page of the contract is at the top.

Click Merge PDF, wait for the download, and open the result before you send it. That last step matters more than it sounds. A quick scroll catches most mistakes.

Windows users often look for a desktop program first. For a one-off merge, the browser is faster. Acrobat and similar tools are useful when you need OCR, redaction or complex forms, but they are overkill for combining a handful of documents.

If the PDFs are password-protected, unlock them in the app that created them. If a file won’t open in Edge, try opening it in a PDF reader. A file that fails in two readers is probably damaged, not a browser problem.

For large files, close other tabs before merging. A 200 MB PDF can work on a recent laptop, but it will be slow on an older machine with 8 GB of RAM.

Mac: same steps, different file picker

Safari, Chrome and Firefox all work. Open the Merge PDF tool, click Select PDF files, and choose the documents in Finder. Reorder them, merge, download.

Preview can combine PDFs, but the workflow is clumsy for more than two files: open both, show the thumbnails, drag pages from one sidebar to the other. It works; it is just slower. For a stack of scans, the browser is less fiddly.

If the result is too heavy to email, run it through Compress PDF. If you only need pages 4–9 of a long report, use Split PDF first and merge the extract with the cover. There is no reason to send 80 pages when the recipient asked for six.

iPhone: the Files app is the real starting point

On iPhone, PDFs arrive in Files from Mail, WhatsApp, iCloud Drive, Google Drive or a scanning app. Open the Merge PDF tool in Safari, tap Select PDF files, and pick the documents from the Files sheet. You can select several at once.

The download behaviour depends on iOS and the browser. Sometimes the merged file opens in a new tab; sometimes it goes straight to Downloads. If you see a preview, use the share button and choose Save to Files. Give it a name you will recognise later.

Phones have less memory than laptops. If the merge stalls, close other tabs, try fewer files at a time, or move to a computer. Merging the first half and then merging that result with the second half is a perfectly reasonable workaround.

The checks that matter before you send

Order is the first thing to verify. Open each source file and note its first and last page. Contracts usually precede annexes; a scanned batch may be reversed. Fix the order in the tool, not after the merge.

Orientation is the second. A landscape spreadsheet inserted into an A4 portrait report is valid PDF, but it prints badly and looks careless. Decide whether to rotate it or export it in the same orientation first. The Rotate PDF tool handles a single page or a whole file; do it before the merge if several documents need rotating.

Blank pages are the third. Scanners add them, especially when someone feeds pages one by one. Use Remove Pages to delete them before merging. The final file will be shorter and easier to review.

Page size is the fourth. A4 and US Letter are close but not identical. If the document must follow a strict format, normalise the pages before combining them. For most everyday uses, mixed sizes are fine.

Finally, open the merged file and scroll through it. Check the joins between documents, not just the first page. A missing signature page is easy to spot at the end and embarrassing to discover after you have sent the file.

Scanned PDFs and OCR

A scanned PDF is a set of images inside a PDF container. Merging works, but the text is not searchable. If the recipient needs to search, copy or index the content, run the merged file through OCR PDF. OCR adds a text layer without changing the visible pages.

Do that after merging. Running OCR on each file first wastes time and can change how the pages are exported. One pass on the final document is usually enough.

Scanned files are also heavy. Twenty colour pages can outweigh a 200-page text report. If email rejects the file, compress it or rescan at a lower resolution. Don’t keep rescanning at 600 dpi “just in case”; 300 dpi is plenty for most documents.

When you shouldn’t merge

Merging is for documents that belong together. It is a bad fit when the recipient needs to sign only one page, when a confidential page should not travel with the rest, or when different departments need separate versions.

In those cases, split the file, remove the pages you don’t need, or send two clearly named files. Two files with clear names are easier to route than one 90-page bundle.

File names, email limits and the last look

A merged PDF called scan_0042.pdf tells the recipient nothing. Rename it before sending: contract-dupont-annexes-2026.pdf is easier to file, easier to find later and less likely to be confused with another submission. If the portal asks for a reference number, put it in the file name.

Most email services cap attachments somewhere between 10 and 25 MB. Merging does not shrink a file; the result can even be a little larger because of the new PDF structure. If the file is too big, Compress PDF is the first thing to try. If the recipient uses a form with a hard limit, check the limit before you spend time compressing.

Send the file to yourself first if it is important. Open it on a phone, not just the computer where you made it. If the pages render there, the recipient is likely to see the same thing. If you have a second reader installed, such as Preview or Acrobat, open it there as well. Different PDF readers occasionally disagree about fonts or annotations.

Passwords, damage and browser memory

A password-protected PDF cannot be merged until it is unlocked. Remove the password in the app that created it, then try again. OpenToola will not guess it, and you should not trust a random site that claims it can.

If a file won’t load, test it in a dedicated PDF reader. If it opens there but not in the browser, try another browser. If it fails everywhere, the file is likely damaged; re-export it from the source application.

When the browser runs out of memory, it may freeze or close the tab without a useful message. Merge fewer files, close other tabs, or switch to a desktop.

What stays on your device

OpenToola does not upload the PDFs. The browser reads them, copies the pages into a new document and creates a download link. There is no server-side copy, no account and no cloud library to clean up later.

That does not make every browser session private by default. Browser extensions can read page content, shared computers can leave downloads behind, and an outdated browser may have vulnerabilities. Use a current browser, avoid merging sensitive documents on a public machine, and delete the downloaded file when you are done.

Tools mentioned

• Merge PDF
• Split PDF
• Compress PDF
• Remove Pages
• Rotate PDF
• OCR PDF
• OpenToola Guides