Issue #1: The font which is used in the report and what is shown on screen as a PDF or Viewer will be different.
Solution: There have been changes that the server might not have that font. If its there, might not be correctly installed.
Try uninstalling that font. Reboot server, install the font again, reboot the server.
If its still not picking up the font, check the permissions on the font folder. The user who runs the Spider (IIS application pool user) might not have permissions to this folder
Issue #2: The font size might be getting reduced or shifted to the left etc
Solution: Your registry might not have the following keys or permission to it.
Go into registry: HKEY_LOCAL_MACHINE\SOFTWARE\Crystal Decisions\10.0\Crystal Reports\Export\PDF and then set a DWORD as ForceLargerFonts to 1
Do the same for HKEY_CURRENT_USER too
Similarly add UsePrecisePositioningForText DWORD with value 1
Check the permissions on the PDF folder in Registry, see whether the user who runs the spider (application pool user) has access permissions.