fix: flatten pdf-lib form fields before sealing document (#2441)

- Fixes checkbox fields not displaying correctly in sealed documents by
calling `flatten()` on the pdf-lib form before saving

packages/lib/jobs/definitions/internal/seal-document.handler.ts

@@ -388,6 +388,10 @@ const decorateAndSignPdf = async ({
       }
     }
 
+    // Should never run into issues with this flatten since all
+    // arcoFields are created by pdf-lib itself.
+    legacy_pdfLibDoc.getForm().flatten();
+
     await pdfDoc.reload(await legacy_pdfLibDoc.save());
   }