No, not directly. PDF (Portable Document Format) files are designed to be read-only and cannot be directly imported into Final Draftfor editing.
If you've received a script as a PDF, you'll be able to open it, read it and print it. If you have to edit, tell the sender to get you the Final Draft file.
If you're sending a script to someone and you don't want them to be able to do anything but read it or print it, send it as a PDF. If you want the recipient to be able to edit, send the Final Draft file.
However, if you have a recent version of the Adobe Acrobat Reader you can go to File > Save As > Text and save the document as a text file:
Import this text file into Final Draft (File > Open) as a script but you may need to do some reformatting. More information on importing material from other programs is here: I imported a script from Word (or another program) and it's all messed up. How do I get it back in shape?