[Zope] Zope / LocalFS ??? PDF files.

Hi there, When a user "uploads" a pdf file using localfs to the server, Zope or LocalFS cuts the file so that just a fraction of the file is stored on the server. All other filetypes are stored OK it is just PDF's that get "trimmed". I'm running Zope 2.3 on a NT-box servicepack 6. Clues anyone ??? With kind regards Fred Rubinstein.