I know I can use *bold*, /italic/, _underlined_, =verbatim= and ~code~, and, if you must, ‘+strike-through+’ to do some markup to text according to org-mode documentation, but they are not enough for me(bold is not obvious when viewing the org file), I know I can customize org-emphasis-alist, but the documentation doesn't tell much. What I want is to highlight the text selected like enriched-mode like the image in this page.
But enriched-mode will save the file as text/enriched format, and I have to use enriched-mode not org-mode itself.
So, how can I re-define or define a new markup(maybe customize org-emphasis-alist) to highlight text like enriched-mode, so
- the highlight is permanent in this file(I can see the highlight in Emacs)
- at the same time it can be exported into pdf or html file.

append, which puts the new element at the end, but we need it at the beginning so it gets found first. Just swap the arguments. The second problem is that it appears to be impossible to add new markup, according to theorg-modemailing list. – erikstokes Dec 30 '14 at 15:26