fix: some pdf font

theme/classic.html

@@ -190,7 +190,7 @@
                         <audio src="<!--FileDownUrl-->" controls="controls" style="width: 100%"></audio>
 <!--IsmusicFileEnd-->
 <!--IspdfFileStart-->
-                        <div id="pdf-d"></div>
+                        <div id="pdf-d">Loading PDF</div>
 <!--IspdfFileEnd-->
 <!--IsofficeFileStart-->
                         <iframe id="office-a" src="https://view.officeapps.live.com/op/view.aspx?src=<!--FileEncodeDownUrl-->" style="width: 100%;height: 800px" frameborder="0"></iframe>
@@ -590,10 +590,16 @@
 <!--IsvideoFileEnd-->
 <!--IspdfFileStart-->
     pdfjsLib.GlobalWorkerOptions.workerSrc = '//cdn.bootcss.com/pdf.js/2.3.200/pdf.worker.min.js';
-    var loadingTask = pdfjsLib.getDocument({ url: '<!--FileDownUrl-->', });
+    var loadingTask = pdfjsLib.getDocument({
+        url: '<!--FileDownUrl-->',
+        cMapUrl: "//cdn.jsdelivr.net/npm/pdfjs-dist@2.2.228/cmaps/",
+        cMapPacked: true,
+        rangeChunkSize: 65535
+    });
     loadingTask.promise.then(function(pdf) {
         var pagenum =  pdf.numPages;
         var pdfContainer = document.getElementById('pdf-d');
+        pdfContainer.innerHTML = '';
         for (var i=1;i<=pagenum;i++) {
             var canvasNew = document.createElement('canvas');
             canvasNew.id = 'pdf-c'+i;