A PDF viewer is a software application that allows users to open, view, and interact with files in the PDF (Portable Document Format) format. These viewers enable users to read documents while preserving the original layout, fonts, and images, making them ideal for sharing and printing. Many PDF viewers also offer features like zooming, searching, and bookmarking. Some popular PDF viewers include Adobe Acrobat Reader, Foxit Reader, and SumatraPDF. Many web browsers, such as Google Chrome and Mozilla Firefox, also have built-in PDF viewing capabilities. These tools are essential for accessing a wide range of documents, from eBooks to official forms.