If you have ever tried embedding EXEs in an existing PDF file using Metasploit, most likely you might have come across the error:
[-] Sorry, I'm picky. Incompatible PDF structure: key not found: "Root". Please try a different PDF template.
Details on the ‘Adobe PDF Embedded EXE Social Engineering’ Metasploit module can be found here.
This is quite an old exploit but still useful in security awareness demonstrations. Recently I had to do one and ran into errors embedding an EXE payload.
To solve the error, open the clean PDF file in Microsoft Word 2013⁄2016 and again save the file in PDF format.
Load the EXE into the modified PDF and it works !!