Paperpile is a free iPhone app designed to help researchers and academics manage their research papers. With Paperpile, users can easily collect, organize, read, and annotate their papers, all in one place.

The app allows users to search millions of papers from over 20,000 academic journals, directly within the app. Adding new papers to your collection is as simple as a tap, with the PDF automatically downloaded. Additionally, users can save papers from their browser directly to their Paperpile library. For those with restricted access to paywalled content, Paperpile supports university off-campus proxy access.

Managing and organizing your library is made easy with Paperpile. Users can create folders and subfolders to bring structure to their library, and visually organize papers with colored labels. Important papers can be marked with stars for easy reference. The search function allows users to quickly find the papers they need.

Reading and annotating papers is a seamless experience with Paperpile's fast and slick PDF viewer. Users can highlight important sections in different colors, add notes to remember key ideas, and even make hand-drawn annotations using their fingers or Apple Pencil.

Please note that a Paperpile account is required to use the app.