From abiword, previewing a document that has fonts less than ten points results in overlapping text. Ghostview doesn't think the resulting printed-to-.pdf files are valid, which only makes sense. I haven't tried this from gnumeric, but given that it has cells separating text, I don't think it'd be a problem there.
I'm guessing this is an AbiWord bug, though I'm not positive about this. I've filed it upstream as: http://bugzilla.abisource.com/show_bug.cgi?id=1761
This has been fixed in AbiWord 0.9.0, so whenever we upgrade to that version, we'll have the fix.
Our current abiword is built without gnome support, so doesn't support page preview, so this is irrelevant. :-(.
(But it would be fixed if we had gnome-print support built in, since we are using AbiWord-0.9.x now.)