PDF Pro 4 is a robust productivity application designed for iPhone users, focusing on reading, editing, and annotating PDF documents. It allows users to highlight text, take notes, and even add voice recordings and photo annotations. The app features a powerful full-text search function, enabling quick navigation through documents and the entire PDF library. Users can import PDFs from cloud services like Dropbox, OneDrive, and Google Drive, and manage files efficiently with folders and color tags.

In addition to its basic functionality, PDF Pro 4 offers premium features that enhance document editing capabilities, such as creating new pages, modifying content, and multitasking with multiple PDFs. The app supports password-protected PDFs and provides a night mode for easier reading in low light. With options for sharing and printing annotated documents, PDF Pro 4 is a versatile tool for anyone needing comprehensive PDF management on their mobile device.