Hi, MathWorker here!
The broken behaviors of Ctrl+F and Ctrl+C in the MATLAB help browser are unfortunately due to a compatibility issue with certain versions of Internet Explorer, in particular IE11 and sometimes IE10. Downgrading your version of Internet Explorer to IE9, which MATLAB R2013b was tested more extensively on, is one way of working around the issue.
You can also work around the Ctrl+C issue by using Ctrl+Insert and Shift+Insert to copy and paste text.
I apologize greatly for the inconvenience! The developers for the Help browser are aware of the issue and actively working on a solution.