diff --git a/src/app/api/pb-files/[collection]/[recordId]/[...filename]/route.ts b/src/app/api/pb-files/[collection]/[recordId]/[...filename]/route.ts
new file mode 100644
index 0000000..b768cae
--- /dev/null
+++ b/src/app/api/pb-files/[collection]/[recordId]/[...filename]/route.ts
@@ -0,0 +1,109 @@
+import { NextResponse } from "next/server";
+
+/**
+ * GET /api/pb-files/[collection]/[recordId]/[...filename]
+ *
+ * Same-origin proxy for PocketBase file responses, so the dashboard
+ * iframe can render PDF slips without the cross-origin
+ * `Content-Security-Policy: ...sandbox` header that PocketBase sets
+ * on `/api/files/...`. That CSP makes the response opaque-origin and
+ * Chromium's PDF viewer silently fails to render the PDF in an
+ * `<iframe>` (downloads still work because they bypass rendering).
+ *
+ * Behaviour:
+ *   - Validates collection, recordId, and filename shape
+ *   - Fetches `${NEXT_PUBLIC_POCKETBASE_URL}/api/files/...`
+ *   - Streams the bytes back with the same Content-Type / Length
+ *   - Strips `Content-Security-Policy` and `X-Frame-Options` so the
+ *     browser will allow same-origin iframe rendering
+ *
+ * Auth: none. PB file rules decide who can read each file; we
+ * enforce the same rule by simply forwarding the URL. Public files
+ * remain public; protected files still require the caller's PB
+ * token, which we currently do not forward (the existing slip
+ * preview only needs public images / PDFs).
+ *
+ * Path: collection in {delivery_notes, purchase_orders},
+ *       recordId is a 15-char PB id, filename is the bare filename
+ *       PocketBase stored on the file field.
+ */
+const ALLOWED_COLLECTIONS = new Set([
+  "delivery_notes",
+  "purchase_orders",
+]);
+
+export async function GET(
+  request: Request,
+  {
+    params,
+  }: {
+    params: Promise<{ collection: string; recordId: string; filename: string[] }>;
+  },
+) {
+  const { collection, recordId, filename } = await params;
+
+  if (!ALLOWED_COLLECTIONS.has(collection)) {
+    return NextResponse.json({ error: "invalid_collection" }, { status: 400 });
+  }
+  if (!/^[a-z0-9]{15}$/i.test(recordId)) {
+    return NextResponse.json({ error: "invalid_record_id" }, { status: 400 });
+  }
+  if (!Array.isArray(filename) || filename.length === 0) {
+    return NextResponse.json({ error: "missing_filename" }, { status: 400 });
+  }
+  // Reassemble the filename from the splat and reject path-traversal
+  // attempts. PB filenames may contain spaces, dots, and underscores
+  // but never `/` or `..`.
+  const joined = filename.join("/");
+  if (joined.includes("..") || joined.includes("\\") || joined.startsWith("/")) {
+    return NextResponse.json({ error: "invalid_filename" }, { status: 400 });
+  }
+
+  const pbUrl = process.env.NEXT_PUBLIC_POCKETBASE_URL;
+  if (!pbUrl) {
+    return NextResponse.json(
+      { error: "pb_url_not_configured" },
+      { status: 500 },
+    );
+  }
+
+  const targetUrl = `${pbUrl}/api/files/${collection}/${recordId}/${encodeURIComponent(joined)}`;
+
+  let upstream: Response;
+  try {
+    upstream = await fetch(targetUrl);
+  } catch (err) {
+    return NextResponse.json(
+      { error: err instanceof Error ? err.message : "upstream_fetch_failed" },
+      { status: 502 },
+    );
+  }
+
+  if (!upstream.ok || upstream.body === null) {
+    return NextResponse.json(
+      { error: "upstream_not_ok", status: upstream.status },
+      { status: upstream.status === 404 ? 404 : 502 },
+    );
+  }
+
+  // Forward only the headers that matter for rendering; strip any
+  // security headers that would prevent same-origin iframe rendering
+  // of PDFs / display of images.
+  const contentType =
+    upstream.headers.get("content-type") ?? "application/octet-stream";
+  const contentLength = upstream.headers.get("content-length");
+  const lastModified = upstream.headers.get("last-modified");
+
+  const headers: Record<string, string> = {
+    "Content-Type": contentType,
+    // Replace PB's inline disposition with a stable filename so
+    // downloads keep the original name. The browser will still
+    // display PDFs inline inside an <iframe>.
+    "Content-Disposition": `inline; filename="${joined.replace(/"/g, "")}"`,
+    "Cache-Control": "private, max-age=300",
+  };
+  if (contentLength) headers["Content-Length"] = contentLength;
+  if (lastModified) headers["Last-Modified"] = lastModified;
+
+  return new Response(upstream.body, { status: 200, headers });
+}
\ No newline at end of file
diff --git a/src/components/slip-preview.tsx b/src/components/slip-preview.tsx
index ccdd23f..4d234aa 100644
--- a/src/components/slip-preview.tsx
+++ b/src/components/slip-preview.tsx
@@ -39,8 +39,18 @@ export function SlipPreview({
       </div>
     );
   }
-  const url = `${PB_BASE_URL}/api/files/${collection}/${recordId}/${encodeURIComponent(filename)}`;
+  // PB serves file responses with
+  // `Content-Security-Policy: default-src 'none'; ...; sandbox`, which
+  // makes Chromium treat the iframe as an opaque sandboxed origin and
+  // silently fails to render PDFs in `<iframe>`. Route the iframe
+  // through our same-origin proxy `/api/pb-files/...`, which forwards
+  // the bytes and strips that CSP, so the PDF actually renders.
+  // Images go directly to PB — `<img>` is not subject to the CSP
+  // sandbox, so the direct URL works there.
+  const pbUrl = `${PB_BASE_URL}/api/files/${collection}/${recordId}/${encodeURIComponent(filename)}`;
+  const proxyUrl = `/api/pb-files/${collection}/${recordId}/${encodeURIComponent(filename)}`;
   const isPdf = filename.toLowerCase().endsWith(".pdf");
+  const url = isPdf ? proxyUrl : pbUrl;
   return (
     <div className="space-y-3">
       {isPdf ? (
@@ -52,7 +62,7 @@ export function SlipPreview({
           />
           <p className="text-xs text-muted-foreground">
             <a
-              href={url}
+              href={pbUrl}
               target="_blank"
               rel="noreferrer"
               className="inline-flex items-center gap-1.5 text-[#F2B165] hover:underline"