diff --git a/App/CLAUDE.md b/App/CLAUDE.md
index 7a40344..8bbc382 100644
--- a/App/CLAUDE.md
+++ b/App/CLAUDE.md
@@ -141,6 +141,8 @@ An **Email to vendor** button on the PO detail (`po-detail.tsx`, available once
 
 The pipeline (no mailto attachment — `mailto:` can't carry files): `prepareVendorEmail(poId)` (`po/[id]/email-actions.ts`) → `renderPoPdf` (`lib/pdf-service.ts`) → **PdfService** (a standalone Express + Playwright microservice, the GstService/EpfoService pattern) renders the existing `/api/po/[id]/export?format=pdf&pdf=1` page to a real PDF via headless Chromium → `uploadBuffer` to R2 (`po-pdf/…`) → `generateDownloadUrl` (presigned, **7-day** TTL) → returns a `mailto:` with the link. The export route accepts a server-only `svc` token (`PDF_SERVICE_TOKEN`) so PdfService can fetch the page without a user session, and `pdf=1` drops the on-screen print button + `window.print()` auto-trigger. Gated by `PDF_SERVICE_URL`/`PDF_SERVICE_TOKEN` — if unset the action returns a friendly "not configured" error. **No new DB model/migration.**
 
+**Caching:** the PDF is stored at a **deterministic per-PO key** (`buildPoPdfKey` → `po-pdf/<poId>/<slug>.pdf`, no timestamp). On each send, `statObject(key)` checks for an existing copy: if one exists and its `lastModified >= po.updatedAt`, it's **reused** (no re-render, no re-upload) and only a **fresh presigned URL is minted** (refreshing the 7-day timer). It re-renders only when there's no copy yet or the PO changed since the cached one.
+
 ### Inventory (feature-flagged)
 
 Inventory (`ItemInventory`, keyed by `productId` + `siteId`) is **incremented at PO approval** — not on close — for the ordered quantities, when the PO has a `siteId`. The whole inventory surface (site stock, consumption) is gated by `NEXT_PUBLIC_INVENTORY_ENABLED` (see `lib/feature-flags.ts`); the vendor/product catalogue used for PO creation stays available regardless.
diff --git a/App/app/(portal)/po/[id]/email-actions.ts b/App/app/(portal)/po/[id]/email-actions.ts
index 64c5c43..bb3844b 100644
--- a/App/app/(portal)/po/[id]/email-actions.ts
+++ b/App/app/(portal)/po/[id]/email-actions.ts
@@ -2,7 +2,7 @@
 
 import { auth } from "@/auth";
 import { db } from "@/lib/db";
-import { buildStorageKey, uploadBuffer, generateDownloadUrl } from "@/lib/storage";
+import { buildPoPdfKey, uploadBuffer, generateDownloadUrl, statObject } from "@/lib/storage";
 import { renderPoPdf, isPdfServiceConfigured, PdfServiceError } from "@/lib/pdf-service";
 
 type Result = { ok: true; mailto: string; to: string } | { error: string };
@@ -47,13 +47,20 @@ export async function prepareVendorEmail(poId: string): Promise<Result> {
     return { error: "PDF emailing is not configured on this environment." };
   }
 
-  // Render → store → presigned link.
+  // Render → store → presigned link. The PDF is cached at a deterministic
+  // per-PO key: if a copy already exists and is at least as new as the PO's last
+  // change, reuse it and only mint a fresh presigned URL (refreshing the 7-day
+  // timer). Re-render only when there's no copy yet or the PO changed since.
   let link: string;
   try {
-    const pdf = await renderPoPdf(poId);
     const slug = po.poNumber.replace(/\//g, "-");
-    const key = buildStorageKey("po-pdf", poId, `${slug}.pdf`);
-    await uploadBuffer(key, pdf, "application/pdf");
+    const key = buildPoPdfKey(poId, `${slug}.pdf`);
+    const cached = await statObject(key);
+    const isFresh = cached !== null && cached.lastModified >= po.updatedAt;
+    if (!isFresh) {
+      const pdf = await renderPoPdf(poId);
+      await uploadBuffer(key, pdf, "application/pdf");
+    }
     link = await generateDownloadUrl(key, LINK_TTL_SECONDS);
   } catch (e) {
     if (e instanceof PdfServiceError) return { error: `Could not generate the PO PDF: ${e.message}` };
diff --git a/App/lib/storage.ts b/App/lib/storage.ts
index 0d6e687..e0e5a04 100644
--- a/App/lib/storage.ts
+++ b/App/lib/storage.ts
@@ -59,6 +59,16 @@ export function buildSignatureKey(userId: string, ext: string): string {
   return `signatures/${userId}.${ext}`;
 }
 
+/**
+ * Deterministic key for a PO's rendered PDF (one object per PO, no timestamp) so
+ * "Email to vendor" can reuse a previously rendered copy instead of re-rendering
+ * and re-uploading on every send (see `prepareVendorEmail`).
+ */
+export function buildPoPdfKey(poId: string, fileName: string): string {
+  const safe = fileName.replace(/[^a-zA-Z0-9._-]/g, "_");
+  return `po-pdf/${poId}/${safe}`;
+}
+
 /**
  * Storage key for a company branding asset (logo or stamp/seal).
  * Deterministic per company+type so a re-upload overwrites the previous file.
@@ -106,6 +116,36 @@ export async function uploadBuffer(
   }
 }
 
+/**
+ * Lightweight existence/metadata check for a stored object (no body transfer).
+ * Returns `{ lastModified }` when the object exists, or `null` when it doesn't.
+ * Used to reuse a cached PO PDF when it's still current.
+ */
+export async function statObject(key: string): Promise<{ lastModified: Date } | null> {
+  try {
+    if (isDev) {
+      const fs = await import("fs/promises");
+      const path = await import("path");
+      const filePath = path.join(process.cwd(), ".dev-uploads", ...key.split("/"));
+      const s = await fs.stat(filePath);
+      return { lastModified: s.mtime };
+    }
+    const { S3Client, HeadObjectCommand } = await import("@aws-sdk/client-s3");
+    const s3 = new S3Client({
+      region: "auto",
+      endpoint: `https://${process.env.R2_ACCOUNT_ID}.r2.cloudflarestorage.com`,
+      credentials: {
+        accessKeyId: process.env.R2_ACCESS_KEY_ID!,
+        secretAccessKey: process.env.R2_SECRET_ACCESS_KEY!,
+      },
+    });
+    const r = await s3.send(new HeadObjectCommand({ Bucket: process.env.R2_BUCKET_NAME!, Key: key }));
+    return { lastModified: r.LastModified ?? new Date(0) };
+  } catch {
+    return null; // missing object (404/NotFound) or any access error → treat as absent
+  }
+}
+
 /**
  * Fetch a stored file as a Buffer (server-side).
  */
diff --git a/App/tests/integration/email-vendor.test.ts b/App/tests/integration/email-vendor.test.ts
index 62f8634..25d919f 100644
--- a/App/tests/integration/email-vendor.test.ts
+++ b/App/tests/integration/email-vendor.test.ts
@@ -17,13 +17,15 @@ vi.mock("@/lib/storage", async (importOriginal) => {
     ...actual,
     uploadBuffer: vi.fn(async () => {}),
     generateDownloadUrl: vi.fn(async () => "https://files.example/po.pdf?sig=abc"),
+    statObject: vi.fn(async () => null), // default: no cached object → render
   };
 });
 
 import { auth } from "@/auth";
 import { db } from "@/lib/db";
 import { prepareVendorEmail } from "@/app/(portal)/po/[id]/email-actions";
-import { isPdfServiceConfigured } from "@/lib/pdf-service";
+import { isPdfServiceConfigured, renderPoPdf } from "@/lib/pdf-service";
+import { statObject, uploadBuffer, generateDownloadUrl } from "@/lib/storage";
 import { makeSession, getSeedUser, getSeedVessel, getSeedAccount } from "./helpers";
 
 const PREFIX = "INTTEST_EMAILVENDOR_";
@@ -98,6 +100,34 @@ describe("prepareVendorEmail", () => {
     expect(decodeURIComponent(result.mailto)).toContain("https://files.example/po.pdf?sig=abc");
   });
 
+  it("reuses the cached PDF on a second send and only refreshes the link (7-day timer)", async () => {
+    as(techId, "TECHNICAL");
+    const poId = await makePo("MGR_APPROVED", vendorWithEmailId);
+
+    // 1st send: no cached object → render + upload once.
+    vi.mocked(statObject).mockResolvedValueOnce(null);
+    expect("ok" in (await prepareVendorEmail(poId))).toBe(true);
+    expect(vi.mocked(renderPoPdf)).toHaveBeenCalledTimes(1);
+    expect(vi.mocked(uploadBuffer)).toHaveBeenCalledTimes(1);
+
+    // 2nd send: a cached object newer than the PO → reuse, no re-render, fresh link.
+    vi.mocked(statObject).mockResolvedValueOnce({ lastModified: new Date(Date.now() + 60_000) });
+    expect("ok" in (await prepareVendorEmail(poId))).toBe(true);
+    expect(vi.mocked(renderPoPdf)).toHaveBeenCalledTimes(1); // unchanged — reused
+    expect(vi.mocked(uploadBuffer)).toHaveBeenCalledTimes(1); // unchanged — reused
+    expect(vi.mocked(generateDownloadUrl)).toHaveBeenCalledTimes(2); // re-presigned each send
+  });
+
+  it("re-renders when the PO changed since the cached copy", async () => {
+    as(techId, "TECHNICAL");
+    const poId = await makePo("MGR_APPROVED", vendorWithEmailId);
+    // Cached object older than the PO's updatedAt → stale → re-render.
+    vi.mocked(statObject).mockResolvedValueOnce({ lastModified: new Date(0) });
+    expect("ok" in (await prepareVendorEmail(poId))).toBe(true);
+    expect(vi.mocked(renderPoPdf)).toHaveBeenCalledTimes(1);
+    expect(vi.mocked(uploadBuffer)).toHaveBeenCalledTimes(1);
+  });
+
   it("is available once payment is recorded too (PARTIALLY_PAID)", async () => {
     as(techId, "TECHNICAL");
     const poId = await makePo("PARTIALLY_PAID", vendorWithEmailId);