How do I add other options to the share icon activity list?

[iMore Question]

If I am in safari and I want to save a document to an app I have -- for example annotate + or cloud on so that I can print it later, currently only social based options are the only ones available when I click the more button. I want to add one or these apps to be able to send the document to the app via share button. But I can't figure out how to add more apps to the activity list that pops up when you click more.

Is this possible?