get statement as file pdf to send in whatsapp template

get statement as file pdf to send in whatsapp template

hello
i have the following url which sends an email with the statement attached 

sendStatement = invokeurl
[
url: "https://www.zohoapis" + dc + "/books/v3/contacts/" + customerID + "/statements/email?start_date=" + start_date + "&end_date=" + end_date + "&filter_by=" + filter + "&organization_id=" + organizationID
type: POST
connection: "zbooks"
];

I don't want to send an email instead I want to send a whatsapp message with the statement document attached so what would be the URL to get the file as a GET method and then I can send it as a parameter to whatsapp template