@Override
public InputStream merge(final InputStream[] sources) {
try {
Assert.notEmpty(sources, "sources");
PDFMergerUtility merger = new PDFMergerUtility();
for (InputStream source : sources) {
merger.addSource(source);
}
ByteArrayOutputStream bos = new ByteArrayOutputStream();
merger.setDestinationStream(bos);
merger.mergeDocuments();
ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
return bis;
} catch (IOException e) {