Read more here – https://www.securelist.com/en/blog/208194129/The_MiniDuke_Mystery_PDF_0_day_Government_Spy_Assembler_Micro_Backdoor
I suggest that you read the following analysis by securelist and apply the suggested counter measures – https://www.securelist.com/en/downloads/vlpdfs/themysteryofthepdf0-dayassemblermicrobackdoor.pdf