clamscan debug information shows the following:
[root@server ~]# /usr/local/cpanel/3rdparty/bin/clamscan --debug MYFILE.pdf 2>&1 | grep -e 'local.ign2' -e 'CVE_2017_3033'
LibClamAV debug: /usr/local/cpanel/3rdparty/share/clamav/local.ign2 loaded
LibClamAV debug: Bytecode 6311970.cbc(60) has logical signature: BC.Pdf.Exploit.CVE_2017_3033-6311970-3.{};Engine:76-255,Target:10;0;2f4a50584465636f6465
LibClamAV debug: Bytecode 6316401.cbc(61) has logical signature: BC.Pdf.Exploit.CVE_2017_3033.{};Engine:76-255,Target:10;0;2f4a50584465636f6465
LibClamAV debug: Bytecode found virus: BC.Pdf.Exploit.CVE_2017_3033
LibClamAV debug: BC.Pdf.Exploit.CVE_2017_3033 found
LibClamAV debug: FP SIGNATURE: a32e841105b6f53a6d85c9d8e57e2cb5:2626574:BC.Pdf.Exploit.CVE_2017_3033
MYFILE.pdf: BC.Pdf.Exploit.CVE_2017_3033 FOUND
So the ignore file local.ign2 is loaded but the signature is still being searched for and found.