Dê uma olhada nisso: Remover informações de texto de um PDF?
Colado aqui para sua conveniência:
Openoffice
Install the PDF Import Extension from Oracle into your Extension Manager for OpenOffice and you will be able to open and edit your PDF files inside of OpenOffice Draw. Which will create all the elements (text, lines, drawings, etc.) and you will be able to remove those that you don't wish. A screenshot is here:
Gimp
If you prefer to handle your pdf pages as layers and edit'em as images, then you can right click the PDF file and choose "Open with GIMP Image Editor", the "Import from PDF" dialog will show after opening gimp and will allow you to choose which pages you wish to edit with several options as shown in the next screenshot.
After which you will also be able to edit those pages as shown in this screenshot:
Good luck!