Portable Document Format (PDF) is a file format used to present documents in a manner independent of application software, hardware and operating systems. A PDF can be opened and annotated in Adobe on a PC and in Preview on a Mac, but no changes can be made to the actual document without special software.
Documents should be in PDF format if they will be opened on the iPad and annotated in a note taking app like Notability. If you are not sure how your students will use a file, save the file as both an Office document and a PDF.
To annotate documents in Preview, click here for the article Mac Preview: Sign documents & View and Edit PDF and Image Files.
Most documents can be saved as a PDF.
To save a file as a PDF
Click on the file menu (or Office button on the PC) > save as