There should be a file called: 0.INTRO.txt
in $path_to/pd/doc/5.reference
If it is not there, it is possible that your installer [if you used one] or you [if you compiled it and put it there yourself] didn't copy that file to the right location. You should locate that file and make sure it is in the right place.
Worst-case scenerio would be that you have to download the PD source and extract that file from the docs there.
Most of your external libraries [zexy, iemlib, gem for sure] should have come with a similar text file, so to have a *complete* list of objects at the click of a mouse, copy all the other texts into this one file.
best, d.