diff --git a/app/config.py b/app/config.py
index 3397773..594b7ef 100644
--- a/app/config.py
+++ b/app/config.py
@@ -1,5 +1,5 @@
 """Application configuration."""
 
-VERSION = "4.7.0"
+VERSION = "4.8.0"
 MAX_FILE_SIZE_MB = 10
 DEFAULT_COLOR = "#ffffff"
diff --git a/app/core/pdf_generator.py b/app/core/pdf_generator.py
index e497460..99e84e7 100644
--- a/app/core/pdf_generator.py
+++ b/app/core/pdf_generator.py
@@ -609,7 +609,7 @@ def generate_pdf(doc) -> bytes:
             c.restoreState()
 
             # If block has a URL, make the entire block a clickable link
-            if getattr(block, 'url', None):
+            if block.url:
                 c.linkURL(block.url,
                           (bx + inset, row_y + inset,
                            bx + bw - inset, row_y + row_h - inset),
diff --git a/app/static/index.html b/app/static/index.html
index a01207d..02cf640 100644
--- a/app/static/index.html
+++ b/app/static/index.html
@@ -7,13 +7,13 @@
     <link rel="preconnect" href="https://fonts.googleapis.com">
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
     <link href="https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&display=swap" rel="stylesheet">
-    <link rel="stylesheet" href="/static/css/app.css">
+    <link rel="stylesheet" href="/static/css/app.css?v=4.8">
 </head>
 <body>
     <header class="header">
         <div class="header-left">
             <h1 class="header-title">Scénář Creator</h1>
-            <span class="header-version">v4.7</span>
+            <span class="header-version">v4.8</span>
         </div>
         <div class="header-actions">
             <label class="btn btn-secondary btn-sm" id="importJsonBtn">
@@ -249,10 +249,10 @@
     <div class="toast hidden" id="toast"></div>
 
     <script src="https://cdn.jsdelivr.net/npm/interactjs@1.10.27/dist/interact.min.js"></script>
-    <script src="/static/js/api.js"></script>
-    <script src="/static/js/canvas.js"></script>
-    <script src="/static/js/export.js"></script>
-    <script src="/static/js/app.js"></script>
+    <script src="/static/js/api.js?v=4.8"></script>
+    <script src="/static/js/canvas.js?v=4.8"></script>
+    <script src="/static/js/export.js?v=4.8"></script>
+    <script src="/static/js/app.js?v=4.8"></script>
     <script>
         document.addEventListener('DOMContentLoaded', () => App.init());
     </script>
diff --git a/app/static/js/app.js b/app/static/js/app.js
index f3d8f26..e50a89d 100644
--- a/app/static/js/app.js
+++ b/app/static/js/app.js
@@ -84,7 +84,18 @@ const App = {
                 date: this.state.event.date_from, // backward compat
             },
             program_types: this.state.program_types.map(pt => ({ ...pt })),
-            blocks: this.state.blocks.map(b => ({ ...b }))
+            blocks: this.state.blocks.map(b => ({
+                id: b.id,
+                date: b.date,
+                start: b.start,
+                end: b.end,
+                title: b.title,
+                type_id: b.type_id,
+                responsible: b.responsible || null,
+                notes: b.notes || null,
+                url: b.url || null,
+                series_id: b.series_id || null,
+            }))
         };
     },
 
@@ -104,7 +115,9 @@ const App = {
         this.state.program_types = (doc.program_types || []).map(pt => ({ ...pt }));
         this.state.blocks = (doc.blocks || []).map(b => ({
             ...b,
-            id: b.id || this.uid()
+            id: b.id || this.uid(),
+            url: b.url || null,           // backward compat: older JSONs lack this
+            series_id: b.series_id || null,
         }));
         this.syncEventToUI();
         this.renderTypes();
diff --git a/tests/test_api.py b/tests/test_api.py
index 4109603..4cf0198 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -185,3 +185,23 @@ def test_backward_compat_date_field(client):
     r = client.post("/api/validate", json=doc)
     assert r.status_code == 200
     assert r.json()["valid"] is True
+
+
+def test_generate_pdf_with_url_block(client):
+    """PDF generation should succeed when blocks contain url field."""
+    doc = make_valid_doc()
+    doc["blocks"][0]["url"] = "https://example.com/linked"
+    r = client.post("/api/generate-pdf", json=doc)
+    assert r.status_code == 200
+    assert r.content[:5] == b'%PDF-'
+    # Verify link annotation is present in the PDF
+    assert b'example.com/linked' in r.content
+
+
+def test_validate_accepts_url_field(client):
+    """Blocks with or without url should both validate successfully."""
+    doc = make_valid_doc()
+    doc["blocks"][0]["url"] = "https://example.com"
+    r = client.post("/api/validate", json=doc)
+    assert r.status_code == 200
+    assert r.json()["valid"] is True
diff --git a/tests/test_core.py b/tests/test_core.py
index fe0fbb5..935f50c 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -22,6 +22,7 @@ def test_block_optional_fields():
     b = Block(date="2026-03-01", start="09:00", end="10:00", title="Test", type_id="ws")
     assert b.responsible is None
     assert b.notes is None
+    assert b.url is None
     assert b.series_id is None
 
 
@@ -31,6 +32,26 @@ def test_block_series_id():
     assert b.series_id == "s_abc123"
 
 
+def test_block_with_url():
+    b = Block(date="2026-03-01", start="09:00", end="10:00", title="Test", type_id="ws",
+              url="https://example.com/test")
+    assert b.url == "https://example.com/test"
+
+
+def test_block_url_in_serialization():
+    """url field must appear in serialized JSON even when None."""
+    b = Block(id="b1", date="2026-03-01", start="09:00", end="10:00",
+              title="Test", type_id="ws")
+    data = b.model_dump(mode="json")
+    assert "url" in data
+    assert data["url"] is None
+
+    b2 = Block(id="b2", date="2026-03-01", start="09:00", end="10:00",
+               title="Test", type_id="ws", url="https://example.com")
+    data2 = b2.model_dump(mode="json")
+    assert data2["url"] == "https://example.com"
+
+
 def test_block_with_all_fields():
     b = Block(
         id="custom-id", date="2026-03-01", start="09:00", end="10:00",
diff --git a/tests/test_pdf.py b/tests/test_pdf.py
index 14dec4c..e4ca187 100644
--- a/tests/test_pdf.py
+++ b/tests/test_pdf.py
@@ -173,3 +173,60 @@ def test_generate_pdf_no_notes_single_page():
     pdf_bytes = generate_pdf(doc)
     pages = len(re.findall(rb'/Type\s*/Page[^s]', pdf_bytes))
     assert pages == 1, f"Expected 1 page, got {pages}"
+
+
+def test_generate_pdf_block_with_url_creates_link():
+    """Block with url should produce a clickable link annotation in PDF."""
+    import re
+    doc = make_doc(
+        blocks=[
+            Block(id="b1", date="2026-03-01", start="09:00", end="10:00",
+                  title="Linked Block", type_id="ws",
+                  url="https://example.com/test"),
+        ]
+    )
+    pdf_bytes = generate_pdf(doc)
+    assert pdf_bytes[:5] == b'%PDF-'
+    # Must contain a /URI annotation with the URL
+    uris = re.findall(rb'/URI\s*\(([^)]+)\)', pdf_bytes)
+    assert len(uris) == 1, f"Expected 1 URI annotation, got {len(uris)}"
+    assert uris[0] == b'https://example.com/test'
+    # Must have a Link subtype annotation
+    assert re.search(rb'/Subtype\s*/Link', pdf_bytes), "Missing /Subtype /Link annotation"
+
+
+def test_generate_pdf_block_without_url_no_link():
+    """Blocks without url should NOT produce link annotations."""
+    import re
+    doc = make_doc(
+        blocks=[
+            Block(id="b1", date="2026-03-01", start="09:00", end="10:00",
+                  title="No Link", type_id="ws"),
+        ]
+    )
+    pdf_bytes = generate_pdf(doc)
+    assert pdf_bytes[:5] == b'%PDF-'
+    uris = re.findall(rb'/URI\s*\(([^)]+)\)', pdf_bytes)
+    assert len(uris) == 0, f"Expected 0 URI annotations, got {len(uris)}"
+
+
+def test_generate_pdf_mixed_url_blocks():
+    """Only blocks with url should produce link annotations."""
+    import re
+    doc = make_doc(
+        blocks=[
+            Block(id="b1", date="2026-03-01", start="09:00", end="10:00",
+                  title="Has Link", type_id="ws",
+                  url="https://example.com/one"),
+            Block(id="b2", date="2026-03-01", start="10:00", end="11:00",
+                  title="No Link", type_id="ws"),
+            Block(id="b3", date="2026-03-01", start="11:00", end="12:00",
+                  title="Also Linked", type_id="ws",
+                  url="https://example.com/two"),
+        ]
+    )
+    pdf_bytes = generate_pdf(doc)
+    uris = re.findall(rb'/URI\s*\(([^)]+)\)', pdf_bytes)
+    assert len(uris) == 2, f"Expected 2 URI annotations, got {len(uris)}"
+    urls = sorted(u.decode() for u in uris)
+    assert urls == ['https://example.com/one', 'https://example.com/two']
