When you receive four separate PDF invoices from a contractor, attaching four separate files to a single email for your accounting department is incredibly annoying and unprofessional. You need to present them as a single, unified, multi-page document. You do not need to purchase expensive third-party software like Adobe Acrobat Pro to merge these files. The native macOS Preview application contains a highly advanced document manipulation engine that allows you to instantly combine, reorder, and merge multiple PDF files directly on your Mac.
Preparing the Document Workspace
To merge files, you must force Preview to expose its hidden structural sidebar, allowing you to literally drag-and-drop pages between documents.
- Double-click the first PDF file (e.g.,
Invoice_1.pdf) to open it in Preview. - Look at the absolute top-left corner of the window. Click the Sidebar Button and select Thumbnails from the drop-down menu.
- You will now see a vertical sidebar on the left side of the screen displaying a tiny preview of every page in the document.
Merging the Files
Now that the structural sidebar is open, you can begin the physical merge process.
- Open a standard Finder window and locate the second PDF file (e.g.,
Invoice_2.pdf) that you want to add to the document. - Click and hold your mouse button on
Invoice_2.pdf. - Physically drag the file from the Finder window directly into the Preview sidebar.
- As you drag it over the sidebar, you will see a green “+” icon appear. You must carefully drop the file exactly where you want it to appear in the pagination sequence. If you want it to be the last page, drop it at the absolute bottom of the thumbnail list.
- Release your mouse button.
The Preview engine will instantly rip the pages out of Invoice_2.pdf and mathematically inject them into Invoice_1.pdf. The sidebar will instantly update to show the new, combined pagination structure.
You can repeat this process as many times as necessary, dragging a dozen different PDF files into the sidebar. Once they are all inside, you can freely click and drag the individual thumbnails up and down to reorder the pages perfectly. Once the pagination is correct, press Command + S to permanently save the newly merged super-document.