File Viewer Plus 4 opens over 400 file formats. View dozens of common file types, such as Office documents, PDFs, and image files, all with one program. Play hundreds of audio and video file formats with the built-in media player. Decompress archives with the file decompression tool. You can also open less common file formats with File Viewer Plus. View Microsoft Project and Visio documents. Open source code files with syntax highlighting. Open email attachments and downloads. If you have unknown files on your PC, try File Viewer Plus.