docs: add section on using JS SDK for downloading files (#16140)

Author: shahednasser

www/apps/book/public/llms-full.txt

@@ -56589,6 +56589,40 @@ The method returns a Promise that, when resolved, has the data returned by the r
 
 ***
 
+## Download Binary or File Responses
+
+By default, the `fetch` method sets the `accept` header of the request to `application/json`, so it parses the response as JSON and returns a JavaScript object.
+
+The `fetch` method decides whether to parse the response as JSON based on the request's `accept` header, not the response's content type. So, if your custom route returns a binary or file response, such as a PDF or an image, you must override the `accept` header to a value other than `application/json`. The method then returns the raw [Response](https://developer.mozilla.org/en-US/docs/Web/API/Response) object without parsing it.
+
+For example, to download a PDF file returned by a custom route:
+
+```tsx
+const response: Response = await sdk.client.fetch(
+  `/admin/orders/${orderId}/invoice`,
+  {
+    method: "GET",
+    headers: {
+      accept: "application/pdf",
+    },
+  }
+)
+
+const blob = await response.blob()
+const url = window.URL.createObjectURL(blob)
+const link = document.createElement("a")
+link.href = url
+link.download = `invoice-${orderId}.pdf`
+link.click()
+window.URL.revokeObjectURL(url)
+```
+
+In this example, you set the `accept` header to `application/pdf`, so the `fetch` method returns the raw `Response` object. You then use the [Response.blob](https://developer.mozilla.org/en-US/docs/Web/API/Response/blob) method to read the response as a [Blob](https://developer.mozilla.org/en-US/docs/Web/API/Blob), which you can download in the browser.
+
+Since the method returns the raw `Response` object in this case, type the returned value as `Response`. You're then responsible for reading the response's body, using methods like `blob`, [arrayBuffer](https://developer.mozilla.org/en-US/docs/Web/API/Response/arrayBuffer), or [text](https://developer.mozilla.org/en-US/docs/Web/API/Response/text).
+
+***
+
 ## Migrating from Fetch API to JS SDK
 
 Prefer `sdk.client.fetch` over the raw [Fetch API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch) when sending requests to your Medusa backend.

www/apps/resources/app/js-sdk/page.mdx

@@ -398,6 +398,44 @@ The method returns a Promise that, when resolved, has the data returned by the r
 
 ---
 
+## Download Binary or File Responses
+
+By default, the `fetch` method sets the `accept` header of the request to `application/json`, so it parses the response as JSON and returns a JavaScript object.
+
+The `fetch` method decides whether to parse the response as JSON based on the request's `accept` header, not the response's content type. So, if your custom route returns a binary or file response, such as a PDF or an image, you must override the `accept` header to a value other than `application/json`. The method then returns the raw [Response](https://developer.mozilla.org/en-US/docs/Web/API/Response) object without parsing it.
+
+For example, to download a PDF file returned by a custom route:
+
+```tsx
+const response: Response = await sdk.client.fetch(
+  `/admin/orders/${orderId}/invoice`,
+  {
+    method: "GET",
+    headers: {
+      accept: "application/pdf",
+    },
+  }
+)
+
+const blob = await response.blob()
+const url = window.URL.createObjectURL(blob)
+const link = document.createElement("a")
+link.href = url
+link.download = `invoice-${orderId}.pdf`
+link.click()
+window.URL.revokeObjectURL(url)
+```
+
+In this example, you set the `accept` header to `application/pdf`, so the `fetch` method returns the raw `Response` object. You then use the [Response.blob](https://developer.mozilla.org/en-US/docs/Web/API/Response/blob) method to read the response as a [Blob](https://developer.mozilla.org/en-US/docs/Web/API/Blob), which you can download in the browser.
+
+<Note>
+
+Since the method returns the raw `Response` object in this case, type the returned value as `Response`. You're then responsible for reading the response's body, using methods like `blob`, [arrayBuffer](https://developer.mozilla.org/en-US/docs/Web/API/Response/arrayBuffer), or [text](https://developer.mozilla.org/en-US/docs/Web/API/Response/text).
+
+</Note>
+
+---
+
 ## Migrating from Fetch API to JS SDK
 
 Prefer `sdk.client.fetch` over the raw [Fetch API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch) when sending requests to your Medusa backend.

www/apps/resources/generated/edit-dates.mjs

@@ -2125,7 +2125,7 @@ export const generatedEditDates = {
   "app/commerce-modules/store/links-to-other-modules/page.mdx": "2025-12-16T06:36:58.256Z",
   "app/examples/page.mdx": "2026-03-27T12:55:32.030Z",
   "app/medusa-cli/commands/build/page.mdx": "2026-06-24T11:05:27.287Z",
-  "app/js-sdk/page.mdx": "2025-12-16T07:15:37.754Z",
+  "app/js-sdk/page.mdx": "2026-07-20T15:06:29.274Z",
   "references/js_sdk/admin/Admin/properties/js_sdk.admin.Admin.apiKey/page.mdx": "2026-04-30T16:36:41.141Z",
   "references/js_sdk/admin/Admin/properties/js_sdk.admin.Admin.campaign/page.mdx": "2026-01-06T15:55:12.396Z",
   "references/js_sdk/admin/Admin/properties/js_sdk.admin.Admin.claim/page.mdx": "2026-04-30T16:36:40.978Z",