You can't. Adobe Reader doesn't do that.
In any case, even 25 MB attachments are much too big for most recipients and can cause severe problems - you will not be thanked for emailing this at all. Yet - people in professional printing may need to send files in the thousands of MB. How do they do it...?
The solution is to use a service designed for sending large files. The file is put away somewhere safely, and a small email is automatically sent with a link to get the big file. There are many services like this, some free for small files like this and some commercial. Adobe have an offering called SendNow, which has a subscription cost. https://www.acrobat.com/sendnow