How do I pdfgrep using a specific pattern (Syntax?)

I'm trying to use pdfgrep to search each occurences of a specific pattern (MUST start with E OR S) then followed by 5 digits (Only) THEN execute a command afterward (Which is likely to be a mv command) So far, I have the following command : pdfgrep -e '[E-S]\d{5,}$' filename.pdf But for the life of me, I am unable to find anything in that PDF. Searching for a specific term (pdfgrep "term" filename.pdf) does return the term in question so I know pdfgrep is able to find it. I am guessing my issue is the syntax of the command or regex but I cannot find where exactly...