No, you can't remove the signature from a PDF file, since this is not available in the Reader application. You will need Adobe Acrobat Professional, which is a shareware application, and a file that permits modifying these parameters. Additionally, you will have to remove the security rights with another application created especially for this operation.
You can get these applications through the database of Software Informer: http://software.informer.com/search/remove+pdf+restriction
