To do it, open the file in Preview, choose File > Export and then select a new file format. If the original is a vector-based logo or illustration, the resulting PDF will also be vector-based (meaning you can enlarge it without losing quality). Remarkably, Preview’s support of native Photoshop (PSD) and Illustrator (AI) files means that you can send either of these native file formats to anyone using a Mac and they can use Preview to open and print them.