A few things to check:
1. Make sure the PDFMAKER.DOT and PDFMAKERA.DOT files are in your
Microsoft Office startup folder.
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?