In some cases, a simple PDF "thumbnail" preview works fine
I think I'm gonna follow this and attach a JPG with every PDF I send.
This said, I'd like to put my thoughts into words about all the software houses which have not yet think about a solution to some common problems raised by many printer & repro houses (eg: overprint preview feature).
Since there are so many plugin developers and acknowledged professionals who try to workaround lots of felt common "problems" in many softwares why the software houses (Adobe above all) don't think to fix them by themselves?
Eg: it took years to Adobe to create a native function in Acrobat for importing an image into a form field - mimicing a well known workaround.
Sorry for my outburst.
PS: by the way... not even Photoshop correctly always handles overprint when importing PDF files.