There are many different Print dialogs but one is very common and is used by Gimp, Shutter, Evloution and Simple Scan. In all these apps the "Page Size" and "Orientation" are disabled. The same dialog in Firefox, Thunderbird and GEdit works OK. I program in Gambas3 which uses this dialog in conjunction with the GTK+ library and it also has these options disabled. If I use the QT4 library then a different print dialog is displayed with no problems. Anybody else notice this problem and found a solution?
Your problem may be due to this issue; https://bugs.launchpad.net/ubuntu/+source/gtk+2.0/+bug/428817
The recommendation is to use the File> Page Setup in Gimp, for simple scan it may be Document> Preferences, Evolution is File> Page Setup as well, check your application of interest for something similar.