I had a requirement of merging two inputstreams of word documents with aspose java
for that I am using
d1 = new com.aspose.words.Document(inputStream1);;
d2 = new com.aspose.words.Document(inputStream2);
InputStream in1 = new FileInputStream("E:\\temp\\in1.docx");
InputStream in2 = new FileInputStream("E:\\temp\\in2.docx");
Document doc1 = new Document(in1);
Document doc2 = new Document(in2);
doc1.appendDocument(doc2, ImportFormatMode.KEEP_SOURCE_FORMATTING);
OutputStream out = new FileOutputStream("E:\\temp\\out.docx");
doc1.save(out, SaveFormat.DOCX);