I need to make a json request which returns a pdf that needs to be saved and sen

As per my understanding of problem - you can use : Send HTTP Request Plug-in - which has a expression to get binary data over http - httpgetbinary() - returns binary response as Base64 String.
The output can be used as input to smartservice in - Base64 Utilities Plug-in - Convert Base64 String to Appian Document Smart Service which then can be used to send by email as attachment.

I can't find this plug-in
Can you please send me the link or indicate me a new method to do that , if it exists ?

Thanks in advance