upload shipping labels from external courier to order metafield

[touchesport]

Through APIs is it possible to upload from courier site the shipping label to the order metafields?

at this moment our courier is connected to our Shopify store through an app

the app is Correo Argentino

the shipping label are created in their site

and we normally download them through their site

so was just wondering if through apis that PDF file can be uploaded to the order