diff --git a/app.js b/app.js
index 38824a1..cfe068f 100644
--- a/app.js
+++ b/app.js
@@ -1834,6 +1834,13 @@ function openFileViewer({ url, blob, mime }, filename, relpath) {
 }
 
 async function openPdfViewer(blob, filename, relpath) {
+    console.log('[PDF] Opening:', filename, 'size:', blob.size, 'type:', blob.type);
+
+    if (blob.size === 0) {
+        showToast('❌ PDF-Datei ist leer oder nicht gefunden', 'error');
+        return;
+    }
+
     const modal = document.createElement('div');
     modal.className = 'fullscreen-modal pdf-viewer-modal';
     modal.innerHTML = `
@@ -1857,25 +1864,37 @@ async function openPdfViewer(blob, filename, relpath) {
     let pdf, currentPage = 1;
 
     try {
-        pdf = await pdfjs.getDocument(new Uint8Array(await blob.arrayBuffer())).promise;
+        const arrayBuffer = await blob.arrayBuffer();
+        console.log('[PDF] ArrayBuffer size:', arrayBuffer.byteLength);
+
+        if (arrayBuffer.byteLength === 0) {
+            throw new Error('PDF-Datei ist leer');
+        }
+
+        pdf = await pdfjs.getDocument(new Uint8Array(arrayBuffer)).promise;
+        console.log('[PDF] Loaded:', pdf.numPages, 'pages');
         pageInfo.textContent = `1 / ${pdf.numPages}`;
 
         async function renderPage(num) {
             if (num < 1 || num > pdf.numPages) return;
             currentPage = num;
-            const page = await pdf.getPage(num);
-            const viewport = page.getViewport({ scale: window.devicePixelRatio });
-            canvas.width = viewport.width;
-            canvas.height = viewport.height;
-            await page.render({ canvasContext: ctx, viewport }).promise;
-            pageInfo.textContent = `${num} / ${pdf.numPages}`;
+            try {
+                const page = await pdf.getPage(num);
+                const viewport = page.getViewport({ scale: window.devicePixelRatio });
+                canvas.width = viewport.width;
+                canvas.height = viewport.height;
+                await page.render({ canvasContext: ctx, viewport }).promise;
+                pageInfo.textContent = `${num} / ${pdf.numPages}`;
+            } catch (e) {
+                console.error('[PDF] Render error on page', num, e);
+                pageInfo.textContent = `❌ Seite ${num} Fehler`;
+            }
         }
 
         await renderPage(1);
         modal.querySelector('#pdf-prev').onclick = () => renderPage(currentPage - 1);
         modal.querySelector('#pdf-next').onclick = () => renderPage(currentPage + 1);
         modal.querySelector('#pdf-download').onclick = async () => {
-            // Download über API mit Content-Disposition: attachment (kein Dialog-Spam)
             const t = await api.getToken();
             const params = new URLSearchParams({ relpath, jwt: t, download: 1 });
             window.location.href = window.location.origin + '/custom/bericht/api/photo.php?' + params.toString();
@@ -1883,8 +1902,9 @@ async function openPdfViewer(blob, filename, relpath) {
         modal.querySelector('#pdf-prev').disabled = false;
         modal.querySelector('#pdf-next').disabled = pdf.numPages === 1;
     } catch (err) {
-        pageInfo.textContent = '❌ PDF-Fehler';
-        console.error('PDF load error:', err);
+        pageInfo.textContent = '❌ ' + (err.message || 'PDF-Fehler');
+        console.error('[PDF] Load error:', err);
+        showToast('PDF-Fehler: ' + err.message, 'error');
     }
 
     modal.querySelector('#pdf-close').onclick = () => {
diff --git a/lib/api.js b/lib/api.js
index 848613b..44a08c1 100644
--- a/lib/api.js
+++ b/lib/api.js
@@ -253,12 +253,15 @@
         const t = await getToken();
         if (!t) return null;
         const params = new URLSearchParams({ relpath, jwt: t });
-        const r = await fetch(API_BASE + '/photo.php?' + params.toString());
+        const url = API_BASE + '/photo.php?' + params.toString();
+        console.log('[API] Fetching file:', relpath);
+        const r = await fetch(url);
         if (!r.ok) {
-            console.warn('getFileBlobUrl failed', r.status, relpath);
+            console.warn('[API] File fetch failed', r.status, relpath);
             return null;
         }
         const blob = await r.blob();
+        console.log('[API] Got blob:', blob.size, 'bytes, type:', blob.type);
         return { url: URL.createObjectURL(blob), blob, mime: r.headers.get('Content-Type') || '' };
     }