Update non-arxiv entries with no pdf

[adamdeller]

I have a bibdesk database which has many entries that lack the pdf version of the paper. I've just discovered adsbibdesk and wish I had earlier, then I probably wouldn't be in this situation, but... Would it be possible to extend the -u option to update any entry which lacks a pdf, regardless of whether it is currently an arxiv listing or not? That would be a really useful feature for half-full databases like mine.