A few things to check:
1. Make sure the PDFMAKER.DOT and PDFMAKERA.DOT files are in
your Word 2003 startup folder. In Word, click on Tools | Options
| File Locations, to see where your startup folder is.
2. In Word, click on Tools | Macro | Security | Security
Level. If your macro security level is set to High, then either
change the security level to Medium, or add Adobe to the list of
trusted sources. See
http://office.microsoft.com/en-us/assistance/HP052356731033.aspx
"Modify the list of trusted publishers for macros" for more
information on how to do the latter.
3. In Word, click on Tools | Templates and Add-ins... under
"Global templates and add-ins", is PDFMaker.dot listed as a
choice, and is it checked?
4. In Word, click on View | Toolbars... is PDFMaker listed as
a choice, and is it checked?