Section 4.4: E-Mail PDF Files
Use the fourth button in the toolbar to attach the PDF that you are currently viewing to an e-mail. This will bring up the in-app mail interface:

Sending an e-mail with PDF attachment
Note that due to memory restrictions in the in-app mail interface, you may be sent back to the "Browse" area before your mail is sent. Of course, you will be returned to the place at which you were reading when you next view your document.
Also, attempting to mail large PDF files may or may not succeed, again due to limitations in the in-app mail interface. If the app crashes during a mail attempt, then this almost certainly means that the PDF file is too large to be handled. (Apple has been notified of this proble and will hopefully address this in a future OS update.)
