It is to make use of the vulnerability of PDF document to cause the system memory overflow error, and then get root permission in the process of error handling, and modify the boot module to gain the final control.

Generally, it exists in the pdf files generated by the lower version of Acrobat, such as the PDF files generated by Acrobat X, which is very difficult, so it is basically only the encryption before version 9.0.

Password opening and remote authentication are difficult to crack, while edited and printed passwords are relatively easy to crack.