feat: 加入上下一页

src/pages/explain/index_pdf.vue

@@ -1,16 +1,15 @@
 <template>
   <!-- pdf_container -->
-  <div class="">
+  <div>
     <pdf
       :src="downUrl"
       :page="pageNum"
       @num-pages="setNumPages"
       @page-loaded="onPageLoaded"
     ></pdf>
-
-    <!-- <p>当前页: {{ pageNum }} / {{ numPages }}</p>
+    <p>当前页: {{ pageNum }} / {{ numPages }}</p>
     <button @click="prevPage">上一页</button>
-    <button @click="nextPage">下一页</button> -->
+    <button @click="nextPage">下一页</button>
   </div>
 </template>