diff --git a/src/app/api/notary/OfficeFolderAnchorsController.ts b/src/app/api/notary/OfficeFolderAnchorsController.ts
index 0a93eb4a..29f9e0ea 100644
--- a/src/app/api/notary/OfficeFolderAnchorsController.ts
+++ b/src/app/api/notary/OfficeFolderAnchorsController.ts
@@ -56,6 +56,7 @@ export default class OfficeFoldersController extends ApiController {
 			const sortedHashes = [...folderHashes].sort();
 			const buffer = await this.secureService.download(sortedHashes);
 
+			response.setHeader('Content-Type', 'application/pdf');
 			this.httpSuccess(response, buffer);
 		} catch (error) {
 			this.httpInternalError(response, error);