ELSE. A PDF file contains one or more page images, each of which can be zoomed in on or out from.PDF files are more than images of documents. They can embed type fonts so that they're available at any viewing location. Interactive elements such as buttons for forms entry and for triggering sound and AVI movies can also be included. PDF is now an open standard, maintained by the International Organization for Standardization (ISO). PDF documents can CONTAIN links and buttons, FORM fields, audio, video, and business LOGIC. It can be signed electronically and anyone can easily view PDF files on WINDOWS or Mac OS using the free Acrobat Reader DC software.