File Conversion from response Link

I am building a WhatsApp chatbot automation , where user will input mobile number and an external http request (POST Request) will be called , In the response api will deliver the pdf link (pdf will be different for each mobile number basically its the invoice of services against that mobile number).I am getting download link  successfully but instead of sending user download link , i directly want to send PDF  ,There should be some option to dynamically convert links to differt file types like to audio,video,PDF , i mean instead of sending dowload links in messages or sending them on emails , files should be directly sent to whatsapp