Update 07/24/2012: Version 6.0.2 is now available in App Store. In this version, the PDF issue is now fixed.
The issue that prevented emailing and opening scanned documents as PDF has now been fixed. The fix has been sent to App Store, and will be out any time soon.
In the meantime, the issue can be easily bypassed by renaming the document before sending or opening it as PDF. When viewing the document, tap “Details”. Touch the “Document title” field. It should read “No title”. Now rename the document and then email or open it normally.