How to combine PDF files in Preview under Snow Leopard

A handy feature of Preview is the ability to open two PDF files and combine them into a single PDF. The method used to accomplish this is different in Snow Leopard than it was in Leopard.

Here is the method to use in Snow Leopard

1. Open each of the individual PDF files. This will result in two or more Preview windows being open, each of which containing a PDF file.
2. Choose which PDF file will be the target file; the one in which all the other PDF files will be added to. PLEASE NOTE: if the PDF target file is actually a JPG image that has been opened in Preview, then you will need to convert the JPG into a PDF first or the combining operation will not be successful. To convert the JPG to a PDF, save it and be sure to choose “PDF” from the “Format” drop-down menu.
3. Ensure that you have opened the sidebar for each PDF window and that the sidebar is in Thumbnail view.
4. Drag the thumbnail of each PDF on top of the thumbnail in the target PDF (the one in which you are combining the PDF’s to.) NOTE: You cannot drag the thumbnail below the thumbnail in the target PDF or the files will not be combined, they will merely be two documents opened in the same window, but when you save the file, they will not be combined but instead will revert to their individual file state.
5. Once you have dragged all the PDF’s to the target PDF window, you can easily rearrange the order simply by clicking and dragging each thumbnail to the order you want.
6. When the order is how you wish, save the PDF. Congratulations. You have just combined multiple PDF files into a single PDF file.

In Leopard, the technique is similar. Instead of dragging the thumbnails on top of the target PDF thumbnail, you merely drop it underneath the thumbnail in the target. Then save as in Snow Leopard.

Here is a brief screencast demonstrating this.