Administration > Environment Variables > APTDEFAULTPDFLINKTYPE — Specifying PDF Links for Web
  
APTDEFAULTPDFLINKTYPE — Specifying PDF Links for Web
Specifies creating links in a PDF file to other PDF files as web links.
If APTDEFAULTPDFLINKTYPE is set to web (case insensitive), links in PDF files to external PDF files will be created as web links. Otherwise, PDF links use a path (which is the default behavior). This environment variable applies only when publishing PDF via the FOSI engine.