We all know that there are a number of attacks where an attacker includes some shellcode in a PDF document. This shellcode uses some kind of vulnerability in how the PDF document is analyzed and presented to the user to execute malicious code on the targeted system.
The following image presents the number of vulnerabilities discovered in popular PDF reader Adobe Acrobat Reader DC, which was released in 2015 and became the only supported Acrobat Reader version after the end of support of Acrobat XI in October 2017. The number of vulnerabilities is increasing over the years. The most important vulnerabilities are the code execution vulnerabilities, which an attacker can use to execute arbitrary code on the target system (if the Acrobat Reader hasn’t been patched yet).