Best way to upload file buffer data and converted into a URL

To be sure do you actually need to store the PDF somewhere persistently? You can use the buffer data as input to a module if it allows mapping that way. But if your module requires a link to grab the file data then yes you’d need to store the the data somewhere. Remember when you’re uploading and downloading data, your data quota will be used on your Make account, and there is a theoretical maximum size that Make will deal with.