Well, I'm not sure how the "Dacons Mailit Plugin:Emai_PopGetAttachment" exactly works.
I do know that PDF's can have that problem when not using the "Insert PDF" or "Insert File" script steps. ("Insert File" I think may only work on Mac, otherwise it shows the icon, as well.)
If you have it filled in already with just the icon, you can script it to export somewhere that's designated for this, and use the "Insert PDF" script step to enter in the field again correctly.
Hope that Helps (HTH)