Thanks so much. Your explanation is brilliant. Easy to follow. Better than apple support itself. :)

OS X comes with a free application called ‘Preview’ that will open automatically whenever you click on a pdf file. Preview can edit and merge pdf files but the official Apple instructions are not quite right. Here’s how to do it depending on which version of OS X that you have.

The basic concept for merging 2 pdf files is the same for whatever version of OS X you have. You open the first file, view the page thumbnails, then drag the second file into the first file and save the new file. Exactly how this works varies depending on which version of OS X that you have. Apple have changed the details a few times. Sometimes there’s a green plus sign to indicate the merge. Sometimes there’s a grey border. If you don’t get it right the 2 files will not merge. You need to read the directions for the exact OS version that you have. (To find out which version of OS X you have just go to the Apple Menu and click ‘about this mac.’)

Please click on the version of OS X that you have to find out how to merge a pdf file:

How to merge PDF files in High Sierra (10.13) (2018)

How to merge PDF files in El Capitan (10.11) (2015)

How to merge PDF files in Yosemite (10.10) (2014)

How to merge PDF files in Mavericks 10.9 (2013)

How to merge PDF files in Mountain Lion 10.8 (2012)

For all versions of OS X prior to Mountain Lion (10.7 and earlier) just follow the instructions below.

Here’s how to join two or more pdf files together using Preview in OS X 10.7 and earlier:

1 Open the pdf file in preview.

2. Open the thumbnail view (Shift-âŒ˜-D)

3. Drag a second pdf ON TOP OF an existing page thumbnail.

When you drag in step 3 it must drag to on top of the thumbnail, as in over it, not above it.

This is a bit hard to explain, the best way to grasp the concept is to look at the pictures below. Can you notice that the thumbnail on the right has an extra grey border compared to the thumbnail on the left. The grey border indicates that the files are merging.

WRONG WAY: If you drag the new pdf file underneath the existing pdf they are not merged.

RIGHT WAY: Drag the new pdf file overlapping an the existing page and they will merge into one – creating one pdf document out of the two. (Notice the extra grey border compared to the left photo.)

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SUMMARY: To combine two separate PDF files into one document you need to drag the new pdf ON TOP OF an existing thumbnail until the grey border appears – then it will merge the two pdfs together. (You can then save the new merged pdf.)

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.

Published Date: March 2008. Last Updated: Dec 2017.

Read on for how to do it step by step.