A commercial library that I would recommend taking a look at is the LEADTOOLS Imaging SDK. The LEADTOOLS Imaging SDK contains support for loading/viewing/manipulating/saving 150+ file formats. Depending on the file formats that you wish to support, LEADTOOLS may be able to allow you to only use one library instead of many different ones saving you time and money.
We have an online hosted HTML5 Document Viewer demo that you can use to view your document or image files:
The LEADTOOLS SDK will allow you to load your files with just a few lines of code in multiple programming languages including C/C++, C#, VB.NET, and Java on Windows. Here is an example in C# using the RasterCodecs class and the RasterImage class:
using (RasterCodecs codecs = new RasterCodecs())
using (RasterImage image = codecs.Load(inputFilePath))
// Your input file is now loaded into memory in the RasterImage object so you can do with it as you wish
// You can load the file into a viewer, process the file, or save the file out to another file format
Just as a disclaimer. I work for the company that wrote this library.