You can split the screen and then hide/show channels as desired (if you had a single busy wavefrom perhaps).
As for opening 2-3 different psdata files in one application, I do not believe this possible (although having two instances of PicoScope6 open is possible to view saved files, I don't think that is what you are asking?).
You could "Edit>Copy Entire Window As Image" and paste into an application like Microsoft Word. Do this for all your saved files and print the Word document?
Technical Author @ Pico Technology UK