Thanks. I was hoping to avoid doing it on the desktop. I'm thinking about/planning to use WP for a website for the English department at my uni. One thing we need is for teachers to uplaod worksheets, tack on notes and instructions, then let students download them. WP could do all that with little fuss, but the students also need visual prompts for what to download. This is in Japan.
We could certainly do what you suggest, but these are English teachers we are talking about. Some people will be OK, but others will have trouble with multiple steps, resizing, etc.
Also, I just found this "* When using ImageMagick, create a thumbnail of a PDF for media browsing (nohn, garvinhicking)" on a page about another php program Serendipity http://www.s9y.org/
Is that what you mean by server limitation? So, maybe if I change hosting companies WP will generate thumbs of pdfs? That would be excellent.