Not quite sure but when saving as PDF there could be issues with the fonts which might be changing 0 to -
Also check if this is happening to other files also OR check your revision scheme for the Vault.
Our title block and more specifically the text defining the revision is Arial, don't think it's font problem.
Although I think I have fixed the issue. I think it was how the Revision variable was defined in PDM. My problem drawings work now, we'll see if the problem reappears...
Thanks for the response Deepak.