Seems that You have to add additional parameter to the GET query. Please read the text below. ¿Can you correct the issue? So we dont have to always add the metadata to the uploaded files.
Using Content-Disposition with Amazon S3
Support for specifying Content-Disposition and Content-Type with S3 destinations is now offered. When these are specified customers can control whether content served from an S3 bucket is opened in the browser, an external player, or downloaded to the user’s desktop. The syntax for specifying content_disposition parameter in the GET query is as follows:
http://[bucket].s3.amazonaws.com/%5Bfilename%5D%5B?acl=public-read | authenticated-read]&content_disposition=attachment
Using this syntax will force the download of the content from the S3 bucket. Please refer to our API Documentation for more information.