How to save a PDF back to an AutoCAD dwg?
This is a very simple process. The key is that you have to have Adobe Illustrator installed on your computer. All you have to do is open the PDF in Adobe Illustrator and save the file as a .dxf file format. Then you simply open the .dxf in AutoCAD.
For other file formats you can simply use the Export menu option to be able to export a pdf document as another file format. In previous versions to Acrobat 8, you would simply do a File-Save As and change the file format type. This is typically used for Word, Html/XML, and Image file formats.
For Excel the process is described in an early blog entry and can be found here.
To prevent other users from using the Export feature you can apply a Permissions Password for your document security that prevents users from extracting the content.
Have fun,
Jonathan