Thanks for your inquiry.
First of all, please note that DocumentExplorer is a very useful tool which easily enables us to see the entire document structure. You can find DocumentExplorer in the folder where you installed Aspose.Words e.g. C:\Program Files (x86)\Aspose\Aspose.Words for .NET\Demos\CSharp\DocumentExplorer\bin\DocumentExplorer.exe. You can observe the DOM structure of your source document with DocumentExplorer. You can also navigate through the DOM hierarchy and insert contents of another Word document at your desired place (Note: Target Node in hierarchy where you want to insert new document must either be a Paragraph or Table Node).
Secondly, you can try appending document to another document by using the following code snippet:
// The document that the content will be appended to.
dstDoc = new Document(MyDir
// The document to append.
srcDoc = new Document(MyDir
// Append the source document to the destination document.
// Pass format mode to retain the original formatting of the
source document when importing it.
// Save the document.
dstDoc.Save(MyDir + “Document.AppendDocument
Please let us know if you need more information, we are always glad to help you.