Download PDF file via API

Hi all,
I wonder if anyone experienced problems with downloading pdf files via API. I have implemented an action API to download a pdf file from an external source, which returns a URL for the file.
Here is how I have tried so far. I have created a workflow (to GET a file via API). Then, I added another step to open “Result of step 1’url” as an external website. However, the file is downloaded with a default “download” name and no file extension. This file can be renamed and opened without any problems if you add a “.pdf” extension. My question is how do I force a proper file download with a name and pdf extension?
API call returns URL as follows: “//s3.amazonaws.com/appforest_uf/f1632182175361x504562336685129000/api_initialize_file”,

My set up looks like this:


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I have tried some pdf viewer plugins, nothing seems to download or open the file properly.

Thanks for your response in advance.