This is what Feedburner did with a PDF file in my weblog feed:
<enclosure url="/studiosetup/ZLVoIPStudio-SysDiag.pdf" length=“23210” type=“application/pdf” />
The original tag that caused this enclosure to be created:
<a href="/studiosetup/ZLVoIPStudio-SysDiag.pdf">
The result of the enclosure looks like this in iTunes:
(See also my earlier post.)