Thanks Michel. The iFrame seems to be the problem indeed. I found the solution by creating a specially formatted URL from the Google Document that eliminates the iFrame limitation.
Replace the last part of the Google Doc URL: edit?usp=sharing with this: pub?embedded=true
For example: https://docs.google.com/document/d/1y71C85KZpy_dpFcakgTxK8lvXZ5SkSJGq5i74vs_dK0/pub?embedded=true
Open it with Tabbed Browser and it will now follow all the links in the document.