code: public NiceXWPFDocument merge(NiceXWPFDocument docMerge) throws Exception {
          if (null == docMerge) return this;
          CTBody body = this.getDocument().getBody();
          String srcString = body.xmlText();
          String prefix = srcString.substring(0, srcString.indexOf(">") + 1);
          String mainPart = srcString.substring(srcString.indexOf(">") + 1,
                  srcString.lastIndexOf("<"));
          String sufix = srcString.substring(srcString.lastIndexOf("<"));
  
          String addPart = extractMergePart(docMerge);
  
          CTBody makeBody = CTBody.Factory.parse(prefix + mainPart + addPart + sufix);
          body.set(makeBody);
          return generate();
      }
docs: 文档末尾合并另一个Word文档
  
  @param docMerge
  待合并文档
  @return 合并后的文档
  @throws Exception
  @since 1.3.0