Devonthink 4 - PDF extraction not working

Firstly, did you read this…

Secondly, DEVONthink 4 can import attachments on its own when importing emails. See the Files > Emails > Automatically import attachments to always import available attachments when you import emails. Or use Tools > Import Email Attachments for selected, already imported emails.

Lastly, the Apple Mail script Add attachments to DEVONthink works for DEVONthink 4.