Answer:
PDF (Portable Document Format)
Explanation:
The PDF file extension indicates that a file is an Adobe Acrobat document. Adobe developed a file format called Portable Document Format (PDF) in the 1990s to display documents that can include images, text, links, buttons, audio, video, form fields etc in such a way that it is not dependent on a specific Operating system, software or hardware.
The PDF file extension is cross-platform which means that the PDF file can be viewed on any Operating System such as Windows, Linux, macOS, Android, IOS etc.