public static void InsertDocument()
{
WordFile wordFile = new WordFile();
WordDocument source = wordFile.Import(File.ReadAllBytes("source.docx"));
WordDocument target = new WordDocument();
WordDocumentBuilder builder = new WordDocumentBuilder(target);
builder.CharacterState.FontSize = 30;
builder.InsertLine("Text start in target document.");
//Insert the source document just after the first paragraph in the target document
builder.InsertDocument(source);
//This line will be appended tight after the source document content
builder.InsertLine("Text end in target document.");
File.WriteAllBytes("InsertDocument.docx", wordFile.Export(target));
}