Unfortunately, we (Adobe Reader mobile team) do not know if/when Apple will fix the attachment problems (software defects) in Apple Mail.
In particular, the attachment problem with Microsoft Outlook (See Problem #2 in How to avoid known PDF email attachment problems) appears to be a long-standing defect that has been known for years. However, Apple has not provided any fix for Apple Mail yet.
Adobe Reader for iOS merely launches Apple Mail (the default mail app on iOS) to send a PDF document as an attachment. Adobe Reader has no control over whether or not to embed a preview image of an attachment in the body of an email message, which is known to cause the problem with Microsoft Outlook (on the receiving side). The same problem happens when you send a single-page PDF document as an attachment along with an email signature from Apple iBooks on iOS.
For now, all iPad/iPhone users can do is to avoid the problems using the workarounds that are described in How to avoid known PDF email attachment problems.