A PDF reader is a software application designed to open, view, 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 readers allow users to read text, zoom in on images, and navigate through pages easily. Many PDF readers also offer additional features, such as highlighting text, adding comments, and filling out forms. Some popular examples include Adobe Acrobat Reader, Foxit Reader, and SumatraPDF. These tools are essential for anyone who frequently works with digital documents.