Create PDF file from image files

Recently, I had to create a PDF file from a lot of image files. Usually, I have to open the image in Preview, then save it to a pdf file. Once I get all the pdf files, combine them together to create one file. It is OK if you are only dealing with a few, but I am facing thousands of them. Finally, I find the Automator( Come with OS X). It is super helpful. Although this is the first time I am working with it, I love it.
Step 1: Select finder items


Step 2: Convert and combine


Step 3: Save as a finder plug in