Open a byte in a DocumentViewer

You'll want to ensure the solution you use supports the file formats you plan on working with. A route you can take is by passing the byte array into a MemoryStream and loading the file using the LoadFromStream method. This will give you a LEADDocument which you can supply into the DocumentViewer. 
 
Here is some sample code and a tutorial which you can supply this into.

byte[] data = File.ReadAllBytes(@"Insert path to file");
using (MemoryStream ms = new MemoryStream(bytes))
{
DocumentFactory.LoadFromStream(ms, new LoadDocumentOptions());
}

https://www.leadtools.com/help/sdk/tutorials/dotnet-winforms-display-files-in-the-document-viewer.html

Part 2:

Once you have added the DocumentViewer control to your WinForm, you can use the following code to display a .doc or .xps file from a byte array: 

// Load the document from the byte array
byte[] fileContents = /* your file contents */;
MemoryStream stream = new MemoryStream(fileContents);

// Create a DocumentViewer and set its Document property
DocumentViewer docViewer = new DocumentViewer();
docViewer.Document = new System.Windows.Xps.Packaging.XpsDocument(stream, System.IO.Packaging.CompressionOption.NotCompressed).GetFixedDocumentSequence();

// Add the DocumentViewer to your WinForm
this.Controls.Add(docViewer);

This code loads the document from the byte array into a MemoryStream, then creates an XpsDocument object from the stream. The XpsDocument object is then used to create a FixedDocumentSequence object, which is assigned to the DocumentViewer control's Document property. Finally, the DocumentViewer control is added to your WinForm's Controls collection.
 

Even though this is a very old post, here is my approach to solve the problem.

Part 1:
To add a DocumentViewer to a WinForm, you can follow these steps:

1. Open your WinForm project in Visual Studio.
2. From the Toolbox, locate the "DocumentViewer" control under the "Reporting" section.
3. Drag and drop the DocumentViewer control onto your WinForm.
4. Resize the control to fit your needs.