What's the best Android app for viewing and annotating PDFs on mobile devices?

Document Viewer is a robust PDF reader that addresses common mobile document management needs with a focus on usability and essential features. For users who frequently handle PDFs on Android phones or tablets, such as students reviewing textbooks or professionals editing reports during commutes, the app provides a suite of annotation tools including highlighters, text comments, and freehand drawing. These features allow for quick markups without requiring a desktop setup. The interface supports smooth zooming and scrolling, even for large files, and includes a night mode to reduce eye strain during extended reading sessions.

A key strength is its form-filling capability, which lets users complete interactive PDF forms directly on their devices—handy for tasks like filling out job applications or surveys while away from a computer. Reviews indicate that the auto-save function prevents data loss, and the file organizer helps keep documents sorted with folders and bookmarks. However, some users report that the free version displays occasional ads, which can interrupt workflow, and cloud storage integration, while present, may not sync as seamlessly as in paid alternatives. For real-world scenarios, such as a freelancer needing to sign a contract on the fly, the app offers basic digital signature support, though advanced features like OCR text recognition are lacking. Despite these minor limitations, Document Viewer remains a dependable choice for everyday PDF tasks, balancing functionality with a straightforward design.