You can go back and edit a Hubpage at any time. Add, delete, revise text. Add or remove capsules, including link capsules.
To answer your question: Yes, you can add in-text content links. The real question is: How many of what type?
Unfortunately, I haven't found SPECIFIC rules that HubPages have published.
But, I gather you can link to many (how many is many) other Hubpages - yours and others - in your HubPages.
There MAY be a two-link limit to other pages outside.
I myself would like specific clarification about that.