Universal Viewer is described as 'advanced file viewer for wide range of formats. Supported file formats are:' and is an app in the Office & Productivity category. There are more than 100 alternatives to Universal Viewer for a variety of platforms, including Windows, Mac, Linux, Android and iPhone. The best alternative is Evince, which is both free and Open Source. Other great apps like Universal Viewer are MPC-BE (Free, Open Source), Bandizip (Freemium), Firefox PDF Viewer (PDF.js) (Free, Open Source) and Xodo (Freemium).
Evince (or GNOME Document Viewer) is a document viewer for multiple document formats: PDF, Postscript, djvu, tiff, dvi, XPS, SyncTex support with gedit, comics books (cbr,cbz,cb7 and cbt) and others. See Supported Document Formats for details.
MPC-BE is a free and open source audio and video player for Windows. MPC-BE is based on the original Guliverkli project and "Media Player Classic Home Cinema" project, contains additional features and bug fixes.
PDF Viewer (aka pdf.js) is a new revolutionary extension using web standard technologies that allows you to display within Mozilla Firefox almost all PDF files found on the web without a plugin. Also available for...
Firefox PDF Viewer (PDF.js) vs Universal Viewer opinions
Xodo is the ultimate cross-platform PDF viewer and annotator. Powerful, fast, and optimized for all phones and tablets, Xodo makes it easy to access, edit, mark up, sort, share, sync, manage, sign, and more with even the most complex PDF documents.
CudaText is a cross-platform text editor, written in Lazarus. It starts quite fast (0.5 sec with ~30 plugins on CPU Intel Core i3 3Hz). It is extensible by Python add-ons (plugins, linters, code tree parsers, external tools).
ACDSee is a complex, multi-purpose application that serves for viewing, organizing and editing digital photos. Furthermore, images can be shared on social websites or your own space on the developer’s website.