A PDF reader is software designed to view, manage, and interact with Portable Document Format (PDF) files. It allows users to open and read documents in the PDF format, which preserves the layout and formatting of the original file across different devices and platforms. Features often include zooming, searching text, highlighting, annotating, and sometimes editing PDFs. Advanced PDF readers may offer functionalities like form filling, digital signatures, and document encryption. The ultimate goal of a PDF reader is to provide a versatile tool for working with PDF documents efficiently and effectively.