Hi glaser13,
Are you opening the PDF file in Reader or Acrobat? Do you see the Sign panel on the right side of the application window? If not, choose View > Show/Hide > Toolbar Items > Show Toolbars.
If all is in place there, it could be that the document is secured and signing isn't permitted. Do you see "(SECURED)" in the title bar?
I look forward to hearing back from you.
Best,
Sara
