iMazing - iMazing lets you transfer music, files, messages, apps and more from any iPhone, iPad, or iPod to a computer, Mac or PC. Manage and backup your iOS device simply without iTunes. (was DiskAid)
Okular - Okular is a universal document viewer based developed by KDE.
Documents by Readdle - A central hub for all your files.
Sumatra PDF - Sumatra PDF is a slim PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows.
FileApp - FileApp is an iPhone and iPad File System and Document Viewer.
Foxit Reader - Foxit Reader is a free and light-weight multi-platform PDF document viewer.