What's the best Android app for quickly highlighting text and adding notes to PDF documents?

Turbo PDF is well-suited for users who need to actively work with PDF documents rather than just view them. The app provides a comprehensive set of annotation tools that enable text highlighting in multiple colors, sticky note placement, freehand drawing, and text insertion. These features prove particularly useful for students reviewing lecture materials, professionals marking up contracts, or researchers analyzing documents. The interface organizes annotation tools intuitively along the bottom toolbar, making switching between highlighters, pens, and note tools straightforward during extended reading sessions. Users report the annotation process remains smooth even with larger PDF files, though some note occasional lag when handling documents exceeding 100 pages. The app automatically saves all annotations, eliminating concerns about losing markups if the app closes unexpectedly. One minor inconvenience involves the slightly small default font size for typed notes, which requires manual adjustment for optimal readability. For document organization, Turbo PDF includes bookmarking and recent file history, helping users quickly return to important annotated sections. The free version covers basic annotation needs, while the premium upgrade unlocks additional markup colors and advanced editing capabilities.