Kingbox.

Kingbox. is a completely free and the most advanced file management app. You can also view and share PDF documents and Office files, save videos and images. A non-stressful offline viewing is available to you anytime, anywhere. Features: -File management (Create folders/Copy/Rename/Protect/Export) -Document viewing (PDF/Office files) -Save, view and browse video/audio/image files -Save Email attachments -Copy from Camera Roll -Decompress files (zip / rar) -Decompress files with password -Output data to external device　 -High security [Supported file formats (e.g.,PDF,PPT,XLS,CSV,DOC,TXT,ZIP,RAR,JPG,PNG,GIF,MP4,MP3,etc.)] -Useful Funections: -Sort files by date,file format,filename,etc. -Misoperation prevention during viewer operation -Zooming In and Out in viewer -Background playback -Create your own playlist -Sleep timer -Playback speed control Use cases: -Carry around files such as proposals and reports -Decompress files on the go -Secure management of critical files -No need to worry about monthly data usage -Never get stressed by the internet environment -Listen to music or watch movies offline -Watch videos during your flight or car ride -Organize pictures in your camera roll -Listen to music while working -Play music you can nod off to sleep to -Make your own playlist -Save your audio studying time by speed listening -Check the movement by slow playback ＼Download the app and try it out／