bookend PDF Viewer is a free Android app developed by iDOC K.K. that allows users to view PDF files on their mobile devices. It can be launched from any file manager app to display PDF files, and it is required to open PDF files from the bookend app.

The app offers various features such as displaying the PDF document, searching for text within the document, displaying the table of contents, supporting links within the PDF, playing embedded videos (mp4), supporting single-page and two-page views (including cover setting), switching between right and left binding, displaying thumbnails, and annotating the document. It is worth noting that with Android 11 and above, security changes prevent direct opening of PDF files from this app. Users are required to select this app when opening PDF files from other file manager apps.

Overall, bookend PDF Viewer is a reliable and easy-to-use app for viewing PDF files on Android devices.