Combining pdf documents on an Apple computer is easy. Leopard and Snow Leopard (the latest versions of Macintosh OSX that come on your computer) have the ability to move pdf pages within a pdf file around and even merge two different pdf documents together. It’s built right in to OS X for free –  you don’t need a third party program to do it!

To join two or more pdf files together using Preview (the standard pdf viewer in OS X) simply open the pdf file in preview, open the thumbnail view (Shift-⌘-D), and then drag a second pdf file ON TOP OF an existing page thumbnail. (It must be on top of the thumbnail, see the pictures below). The two documents will merge into one. Then save the new combined file. Read on for step-by-step instructions.

SUMMARY: To combine two seperate PDF files into one document you need to drag the new pdf ON TOP OF an existing  thumbnail and it will merge the two together. 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. See these two pictures below to visualise the difference.

Drag the new pdf file under the existing one and it will insert a thumbnail that links to the second pdf but they are not merged.

Drag the new pdf file on top of the existing one and it will merge into it - creating one pdf.

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The blue line that appears underneath the original pdf lets you know the files are NOT being combined. Move the pdf on top of the other pdf so that the blue line disappears.

Here’s how to do it step by step.

1. Firstly, open one of the pdf files in Preview. Preview is the default application that a pdf will open into so if you just double click on the pdf file it will open in Preview.

2. Now go to the menu at the top of the screen called ‘View’ and click on ‘Sidebar’ (or  ‘Show Sidebar’ if you have Snow Leopard). Alternatively, press Shift-Command-D to show the thumbnails. This will make a sidebar appear on the right side of the window with thumbnails of all the pdf pages in it. (See these pictures below).

In Leopard select 'Sidebar'

In Snow Leopard and newer versions of Preview select 'Sidebar' then 'Show Sidebar'

3. You can now drag the second pdf file (from a folder or from your desktop) into this sidebar window, and it will be added to your pdf document as an additional page.

Drag the new pdf from the desktop onto an existing thumbnail.

To merge the two files you need to drag the new pdf ON TOP OF an existing  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. See these two pictures below.

Drag the new pdf file under the existing one and it will open but not merge.

Drag the new pdf file on top of the existing one and it will merge.

In some older versions of Preview, if you drag the second file on top of an existing page in the sidebar, it will appear as a red box to show you it will be merged, or as a red line to show you it will not be merged.  In the latest version of preview, the red box does not appear, but the same principle applies – drag it on top of the existing thumbnail to merge the two documents.

You can now save it – use ‘save as’ to save a new document with the merged fles, or you can use use ‘save’ to save over the existing document, adding the new pages to it.

No – you can’t reduce  the file size of the new PDF document –  you can’t get everything for free! To do this you Adobe Acrobat Professional.

Like this article ? Click here to for how to make a pdf booklet. Also here for how to reduce the file size of a pdf.