A PDF Viewer is a software application designed to open, view, and interact with files in the PDF format. These viewers allow users to read documents while preserving the original formatting, making them essential for sharing and reviewing files across different platforms. In addition to basic viewing capabilities, many PDF Viewers offer features such as annotation, highlighting, and form filling. Popular examples include Adobe Acrobat Reader and Foxit Reader, which enhance user experience by providing tools for collaboration and document management.