How do we remove some paper sizes that are not going to be used while creating new ones?
I was able to remove paper sizes by removing them from the PDFCREAT.PDD file in {Windows}\\System32\\spool\\drivers\\x64\\3 and then saving the file. This file might be in a slightly different folder for different versions of Windows. If you're using Vista or later, you'll probably need to start Notepad or whatever editor you use with administrator rights (right click the launch icon and select Run as administrator).
I also added papersizes in the above file, but they did not seem to be available to PDFCreator until after I rebooted my computer.
Yes I can remove paper sizes by editing that file, but I cannot add them, not even after rebooting.
After doing so, the menu in Advanced PDFcreator options only shows the remaining paper size. But this makes no difference, since the selection in that menu is always ignored. I haven't found out how to select a paper sice yet.