Yes, because there are ways to trigger a malware install or Viruses using a PDF files.
Example:
* https://www.welivesecurity.com/2018/05/15/tale-two-zero-days...
(a remote-code execution vulnerability in Adobe Reader and a privilege escalation vulnerability in Microsoft Windows triggered via PDF)
* https://blogs.quickheal.com/beware-pdf-attachments-launching...
(PDF's launching Android Malware)
* https://www.sans.org/security-resources/malwarefaq/pdf-overv...
(A slightly dated FAQ on PDF Malware)