To make a PDF file editable firstly remove restrictions from it. For that, you can try SysTools PDF File Unlocker Tool. With this software PDF files can be unlocked for editing, printing, copying, signing, etc. Once the software removes editing restrictions you can easily edit PDF files using any editor. To know the complete working of the software watch this video. The tool is available for both Windows as well as for Mac users.
It has been developed by a Microsoft Certified Software Consultant (CCS) and can be freely downloaded in English and German (the two languages the latest version supports).