Make page rotation and crop undoable. Don't change the document change count, as this is not persistent. 
Make page rotation and crop undoable. Don't change the document change count, as this is not persistent. 
ycaihua/skim-app,WoLpH/skim,WoLpH/skim,ycaihua/skim-app,ycaihua/skim-app,ycaihua/skim-app,WoLpH/skim,WoLpH/skim,WoLpH/skim,ycaihua/skim-app