How the recipient sees the file and how you see it when you add it to the email are unrelated.
Yes, if the PDF is a single page PDF, it automatically shows it in the body of the email you are composing, if it has 2 or more pages, it will be shown as a file icon attached to the body of the email instead. However, whether the recipient sees it as such or as just an attachment, is controlled by whatever email client they are using.
Apple's own default email app in its devices, will show it in the body of the email, other email clients like outlook, or Thunderbird, will very likely simply show it as an attachment outside the actual email.
How the recipient then saves the attachment, is not for you to control. Each recipient should be capable of saving the attachment by whichever method their email client provides regardless of how you see it.
There is no control over this, and there does not need to be, since any control you may have would only be local to you, and have no effect on how the recipient's email client chooses to display the attachment.