How To: Combine PDFs on Mac OS X

OS X provides a pretty handy way of combining PDFs in Preview. Go Menu -> View -> Contact Sheet with both files, and drag additional PDF pages onto the first one. However, sometimes it just doesn’t seem to work.

When there’s only a single page of the first PDF, we need to drop the new pages right on top of the first one’s thumbnail, otherwise it’ll just be a preview window of 2 PDF files.