In Photoshop, go to File > Automate > PDF Presentation. In the PDF Presentation dialog that appears, add your images. If they are ones that are already open, select "Add Open Files." If they're not open, you can click Browse... to navigate to the images. When you have all the images added, look at the right side of the dialog under Output Options. Change from the default of Multi-Page Document to Presentation and adjust the options as needed. In the Presentation Options below that, you can adjust the duration of each image in the presentation. The default time is 5 seconds.