The PDFMaker may have been disable in your Outlook.
To enable it open Outlook.
Click on > Tools > Trust Center
Choose Add-Ins in the list on the left side of the Trust Center window. Choose Disabled Items in the Manage pop-up menu at the bottom of the Trust Center window. Click Go.
Look in the Disabled Items list for Acrobat PDFMaker Office COM Add-In.
If Acrobat PDFMaker Office COM Add-In is in the list, then select it, click Enable, and click Close. Then close and reopen the Office 2007 application.
Hope this will resolve your issue.
Thanks! PDFMaker was not specifically disabled, but it was not on the Active Application Add-Ins list either, so I added it and now I have my Convert to PDF option back.