This is a free app that is similar to iMovie. For an additional $.99, you can have full capabilities of adding photos, music, voice over, and transitions.
Wondershare lets you edit PDFs from a Mac. It is less expensive than the full version of Acrobat. A great classroom example came from an EdTechTeacher summer workshop participant. She created a Wordle, which she saved as a PDF. Then she inserted a QR code into it that linked back to additional information on her blog.