# How to merge several PDFs into one, for free > On Mac and iPhone, Preview is enough, and it is already built in. On Windows you need a program: PDFsam Basic is free, open source and works on your computer without uploading your documents to the internet. Source: https://simplebuild.it/tutorial/unire-pdf Author: SimpleBuild, Build simple. Deliver value. Category: PDFs and documents Procedure verified on: 2026-09-29 On **Mac** and **iPhone** you don't need to install anything: you use **Preview**, the app that is already built in. On **Windows** there is no built-in tool to merge PDFs, but there is **PDFsam Basic**, free and open source, which works on your computer without sending your documents over the internet. ## Before you start - **Make a copy of the original PDFs.** Preview saves changes automatically: if you merge the files directly, the original changes. Apple recommends duplicating them first. - **Be careful with sites that merge PDFs online.** They are handy, but to work they need to receive your documents. If these are ID documents, health data, contracts or payslips, you are handing personal information to a service you don't know. A tool that works on your computer, like the ones in this guide, is better. - Decide **the order** you want the documents in: it is easier to sort it out beforehand. - If the sheets are still on paper, first turn them into PDFs with the guide on [how to scan a document](https://simplebuild.it/tutorial/scansionare-documento). ## On Windows 11 and 10 with PDFsam Basic PDFsam Basic is a free and open source program (AGPL license), for Windows, macOS and Linux. Its website states that files are processed on your computer and are never uploaded to any server. ### Downloading it 1. Go to the official page [pdfsam.org/download-pdfsam-basic](https://pdfsam.org/download-pdfsam-basic/). 2. In the **Windows** section choose **MSI installer 64-bit (.msi)**. The first button at the top, the "Windows downloader", also offers to try the paid version PDFsam Enhanced: if you are not interested, use the MSI installer. 3. Open the downloaded file and complete the installation. You need Windows 10 or later, 64-bit. ### Merging the PDFs The official page describes merging in four moves: 1. Open PDFsam Basic and choose the **Merge** tool. 2. **Drag** the PDFs you want to merge into the window. 3. **Put the files in the order** you want in the final document. 4. **Choose the name** and the folder of the PDF that will be created, then press **Run**. The merged PDF appears in the folder you chose. Open it and check that all the pages are there, in the right order. Among PDFsam Basic's options there are also a table of contents and a way to make the page sizes the same: useful, but not essential. ## On Mac with Preview 1. If you want to keep the originals, open each PDF and choose **File > Duplicate** to make a copy. 2. Open the PDFs you want to combine in **Preview**. 3. In each open PDF choose **View > Thumbnails**: the pages appear small in the sidebar. 4. **Drag the thumbnails** from the sidebar of one PDF to the sidebar of the other. You can put them at the end or between two pages. To pick several that are not next to each other, click while holding down the **Command** key. ![Preview on Mac: a page thumbnail is dragged, along the blue arrow, from the sidebar of one PDF to the sidebar of the other.](https://simplebuild.it/assets/img/tutorial/unire-pdf-mac-miniature-en-814.webp) (Image: [Apple Support](https://support.apple.com/en-us/guide/preview/prvw43696/mac)) 5. Drag the thumbnails to **reorder** them as you like. To add a whole PDF to another one, drag the file's icon from the Finder to the sidebar of the open document. ### Even faster: from the Finder 1. Open a **Finder** window and select the files to merge, **in the order** you want them: the PDF puts them in the same order you selected them. 2. Click the selected files while holding down the **Control** key. 3. Choose **Quick Actions > Create PDF**. ![Diagram of the Finder: three files selected and, after a Control-click, the Quick Actions menu with the Create PDF option.](https://simplebuild.it/assets/img/tutorial/unire-pdf-finder-crea-pdf-en.svg) The new PDF is created in the same folder, with a name similar to that of the first file. ## On iPhone with Preview On iPhone with iOS 26 or later there is the **Preview** app, which lets you insert one PDF into another. 1. Open the **Preview** app and open the first PDF. 2. Tap the **page count** to see the thumbnails. If you don't see it, tap the PDF first. 3. Touch and hold a thumbnail until the menu appears. 4. Tap **Insert from File** and choose the second PDF. 5. To move a page, touch and hold it until the menu appears and drag it above or below another page. ## On Android On Android there is no built-in procedure that works on every phone, and the apps change from brand to brand. If the document is important, the simplest and safest way is to merge the files on the computer with one of the methods above. Avoid unknown apps or sites that ask you to upload your documents. ## If it still doesn't work - **The final PDF is too heavy to send by email**: follow the guide on [how to reduce the size of a PDF](https://simplebuild.it/tutorial/comprimere-pdf). - **A PDF is password-protected**: you need to know the password and open it before you can merge it. Don't use programs that promise to "unlock" it. - **The pages have different sizes** (A4 and receipt slips, for example): that is normal. PDFsam Basic has an option to make them uniform. - **After merging you have to sign the document**: see [how to sign a PDF](https://simplebuild.it/tutorial/firmare-pdf). - If you often have to merge, split and rename dozens of documents, a small automation can be set up to do it for you: it is the kind of job where a technician saves you hours. ## Frequently asked questions ### Can I use one of the many sites that merge PDFs online? Technically yes, but you upload your documents to someone else's server. For ID cards, payslips, medical reports or contracts, a tool that works on your own computer is better. ### Can the free Acrobat Reader merge PDFs? According to Adobe's website, the free Reader is for viewing, filling in, signing and commenting; merging PDFs is part of the paid tools. ### Can I change the order of the pages after merging them? Yes. In Preview, on Mac and iPhone, you drag the page thumbnails to the right place. With PDFsam Basic it is best to sort the files before merging them. ## Sources - [Combine PDFs in Preview on Mac (Apple)](https://support.apple.com/en-us/guide/preview/prvw43696/mac) - [Combine files into a PDF on Mac (Apple)](https://support.apple.com/en-us/guide/mac-help/mchl21ac2368/mac) - [Add, delete, rotate, move, or crop PDF pages in Preview on iPhone (Apple)](https://support.apple.com/en-us/guide/iphone/iphbf4977cff/ios) - [Merge PDF files (PDFsam)](https://pdfsam.org/pdf-merge/) - [Download PDFsam Basic (PDFsam)](https://pdfsam.org/download-pdfsam-basic/) - [Acrobat Reader (Adobe)](https://www.adobe.com/acrobat/pdf-reader.html)