How do I combine two or more images to get a single pdf file?
Here are the steps to save multiple images in Preview into a single multi-page PDF.


Select all of the images you want in your PDF, right-click and choose open with Preview
In Preview's Sidebar drag the images into the order you want them to appear in your PDF
Select/highlight all the images to be included in the PDF document; otherwise only a single image may end up the PDF document
Then from the "File" menu choose "Print Selected Images" (or "Print..." in recent OS X versions) and then "PDF > Save as PDF"