there is a documentation (pd-msg_05) about internal msgs to pd, but it's quite old and refers to pd_0.34. but i think the most examples still work.
i think, i'm using the pd since 0.35 ... and i doubt that anything concerning internal messages (to pd or to canvases) has changed since then ...
still, the only really useful internal messages are messages to pd ... before starting to mess with messages to canvases to do dynamic patching, i'd propose use dyn~, since it's dynamic patching capabilities are way advanced ...
by the way: is there another of way to find all possible msgs besides reading the c-code? if yes, i might be interested in making an update of this docu.
run "pd -d 2" and have a look at the console output (stderr, not the gui console) ... i've also prepared some example patches for my workshop at the lac3, but it's not really covering more that the docs you mentioned ...
cheers .... tim