A PDF viewer is a software application designed to open, display, and interact with files in the PDF (Portable Document Format). This format is widely used for sharing documents because it preserves the original layout, fonts, and images, making it look the same on any device. PDF viewers allow users to read, print, and sometimes annotate these documents. Many PDF viewers are available, ranging from simple applications to more advanced ones with editing features. Popular options include Adobe Acrobat Reader, Foxit Reader, and various web-based viewers. These tools help users access important documents easily and efficiently.