It's really easy to combine PDF files on Mac OS X. Both Leopard and Snow Leopard have the ability to move pdf pages around and even merge two pdf files together. What's more, the Preview is built right in all Mac OS X – you don’t even need a third party software to combine PDFs on Mac OS X.
Case 1, combine two PDF files on Mac
To combine two or more PDF files together using Preview (the standard PDF viewer in all Mac OS X),
First, simply open the PDF file in preview;
Second, open the thumbnail view (Shift-Command-D)
Third, drag a second pdf file ON TOP OF the existing page thumbnail. NOTE: The second opend PDF file must be on top of the first opened thumbnail. If you drag it into the sidebar but not on top of an existing page the new file will be added as an external link – not merged into the original pdf document.
Fourth, combine two PDF files into one.
Case 2, merge many PDFs on Mac
To merge more PDFs on Mac OS X, you can follow below simple tutorial step by step:
1. Open the PDF documents that you want to combine in Preview.
2. Show the sidebar in each Preview window. If the sidebar is not showing, click the Sidebar button in the Preview window's toolbar, or choose View > Sidebar > Show Sidebar.
3. Verify that the sidebar is configured to show thumbnails (this the default view). If the sidebar is not showing thumbnails, choose View > Sidebar > Thumbnails.
4. Drag the thumbnail of one PDF (source) over of the thumbnail of the other PDF (destination) and release the mouse or trackpad button when the pointer shows a Green Circle with a plus symbol in it. This will copy all pages from the source PDF and add them to the end of the destination PDF.
Tips: 1) You can merge specific PDF pages with another PDF document, select only the pages you want to copy and drag them over the destination PDF document's thumbnail.
2) If the destination PDF has multiple thumbnails showing in the sidebar, you can also add specific PDF pages to any part of the destination PDF, just drag the copied pages to the precise location where you want the pages added. And a blue bar will appear between the pages where the copied pages will be inserted.
5. If the pages in the destination PDF are shown in the wrong order, click the gray circle containing an arrow that appears over the PDF document's thumbnail, so that the arrow points to the right, and drag the thumbnails of the individual pages into the desired order.
6. After the destination PDF contains all of the pages you want and the pages are in the correct order, you can select File > Save As to save a new PDF document containing all of the combined pages, or you can select File > Save to replace the original version of the destination PDF with the version containing the combined pages.
Tips: The Save or Save As commands will only save the document currently being viewed in the window, not all documents shown in the sidebar.
Just repeat above process to combine many PDFs on Mac OS X.
If you have another Windows computer, you can easily combine PDF files with a PDF merger.