This might be perhaps a bug in Reader, or not. When you view "this version" the view presented in Reader has limited capabilities. Perhaps attachments are one of the limitations of this view. If you save "this version" (with a different name or in a different location) and reopen saved PDF your attachment reappears.
Thanks isakten - nice catch with saving and re-opening.
Unfortunately, our customers are not really happy with this Acrobat's glitch, as they need some kind of 'proof' that the embedded files *are* actually covered by the signature (and this point of view is completely understandable). The save-and-re-open trick might help, though ideally we would prefer some 'statement' from Adobe official which we could use to refer our customers to.
We've also got another issue of a similar kind with viewing signed documents containing files embedded as annotations, but I'm going to submit that to another topic a bit later today.
"View this version" comes with a disclaimer in the top bar that most functions are disabled in this view. If attachments are shown in the "Attachments" panel, then they can be opened
(otherwise what's the point to show them at all), and Acrobat uses a default app for this MIME type (i.e. Notepad for .txt files) to open it and has no control what the user could do there. User could definitely copy this file to a different location and this is akin to copying some of he PDF's content which is a prohibited operation in this view.
You can treat the disclaimer in the top bar as the Adobe official statement along with my read on what it means with respect to annotations.
IMO to "View this version" for the last signature when there are no changes after the file was signed is meaningless because both versions are identical. It is only when some changes were made after a signature that you may want/need to view the signed version.
Sounds reasonable, thanks. And if we dare to recall that the embedded files feature is actually described in the 'Interactive Features' chapter of the PDF specification (and all interactive features are disabled, according to the warning panel at the top), we'll get a pretty viable formal argument that the files must not be shown in that view.
Feeling like a lawyer looking for a loophole in a dumb 200 year old law in order to substantiate the obvious .