Is it possible to add several plots to the same PSpice simulation?
I was browsing the unanswered questions like Vlad did (see the comment above), so... - maybe it's too late, but what if it can still help... ;-)

This problem can be solved (in PSpice) using command file(s) the following way:


After a simulation delete all traces in the Probe window (don't use any probes within the simulated circuit schematic; the Probe window is empty then)
Use PSpice Probe Menu/File/Log Commands...
Choose a directory and a name for a command file. Its default extension is cmd; but it's a text (macro) file.

From this time on all commands are recorded in the above file unless you stop it by:

PSpice Probe Menu/File/Log Commands... (using the same menu item as before).

During the recording you can insert required traces, make calculations with trace variables, insert new plots, etc.

After that (when recording has been stopped), the recorded commands can also be edited in a ("pure") text editor. So, when you comprehend the principle by exploring the recorded commands in that file (it's quite easy), you can do "whatever you want" with them  (what is allowed, of course ;-), add some new by hand, etc... (or do nothing, it's up to you). 
Their use is easy: 

a) Start with an empty Probe window (don't use any probes within the schematic diagram)

b) Use PSpice Probe Menu/File/Run Commands...

Select the appropriate command file (you can have created more than one for one simulation, of course) and...


...that's it.