由于poi-tl横向和竖向页合并会出现问题，改用spire.doc解决

用到的依赖：

<dependency>
   <groupId>com.deepoove</groupId>
   <artifactId>poi-tl</artifactId>
   <version>1.10.0</version>
</dependency>

<dependency>
   <groupId>e-iceblue</groupId>
   <artifactId>spire.doc.free</artifactId>
   <version>3.9.0</version>
</dependency>

@SneakyThrows
@org.junit.jupiter.api.Test
public void test5(){
    InputStream head = new FileInputStream("C:/Users/usher/Desktop/1.docx");
    XWPFTemplate headTemplate = XWPFTemplate.compile(head).render(new HashMap<>());//根据关键词填写模板
    NiceXWPFDocument headTemplateXWPFDocument = headTemplate.getXWPFDocument();
    InputStream main = docToDocx(new FileInputStream("C:/Users/lishu/Desktop/11.doc"));
    com.spire.doc.Document headDocument = NiceXWPFDocumentToDocument(headTemplateXWPFDocument);
    com.spire.doc.Document mainDocument = new com.spire.doc.Document(main);
    SectionCollection sectionCollection = mainDocument.getSections();
    Section lastSection = headDocument.getLastSection();
    for(int i=0;i<sectionCollection.getCount();i++){
        Section section = sectionCollection.get(i);
        if("Portrait".equals(sectionCollection.get(i).getPageSetup().getOrientation().toString())){
            //竖版
            section.cloneSectionPropertiesTo(lastSection);//这一行是为了保留合并文件的页码
            sectionCollection.get(i).getBody().getChildObjects().forEach(o -> {
                lastSection.getBody().getChildObjects().add(((DocumentObject) o).deepClone());
            });
        }else{
            headDocument.getSections().add(sectionCollection.get(i).deepClone());
        }
    }
    headDocument.saveToFile("C:/Users/usher/Desktop/2.docx");
}

public com.spire.doc.Document NiceXWPFDocumentToDocument(NiceXWPFDocument niceXWPFDocument) throws IOException {
    ByteArrayOutputStream os = new ByteArrayOutputStream();
    niceXWPFDocument.write(os);
    InputStream is = new ByteArrayInputStream(os.toByteArray());
    com.spire.doc.Document document = new com.spire.doc.Document();
    document.loadFromStream(is, FileFormat.Docx);
    closeStream(is);
    closeStream(os);
    return document;
}