One such minor tweak is the ability to change the paper size in Plus. If you go to the Page Setup screen, you will see that there is now a dropdown available for the paper size.
Change the paper size in Plus. You would need to save the worksheet to persist those changes.
Open the worksheet in Viewer; click the 'Printable Page' link and click the 'Page Setup' tab.
And it works the other way too (i.e. change paper size in Viewer, and it is picked up by Plus).
You do need to save your worksheet first. How do you know you need to save? A little asterisk next to the worksheet name tells you that the worksheet has been changed and that you need to save to persist those changes. If you are not the owner of the worksheet, you would only see a 'Save as' link.
Once saved, open the worksheet in Plus to verify that the changes are indeed displayed.
Note: Phase 2 of the App Server is 10.1.2.0.2, but the major version number of Discoverer is actually 10.1.2.1.0 (I covered this in an earlier post).