Don't go through the Library. Manually look for the files in the Finder: They should be in Home-> Shared or whatever folder has been specified as shared in Limewire->Options->saving. Go there and try opening them thru there.
I've never tried opening .pdfs myself so it may be that LW does not open these (like it does not open apps)

__________________
iMac G4 OSX 10.3.9
RAM 256MB
LW 4.10.5 Basic
ADSL anything from 3 to 8Mbps/around 1024kbps

"Raise your can of Beer on high
And seal your fate forever
Our best years have passed us by
The Golden Age Of Leather"
-Blue Öyster Cult-