Override method to determine the document type from a file. If it's a type we can't open, try to check for the file header, it might be PDF or PS with the wrong extension. 
Override method to determine the document type from a file. If it's a type we can't open, try to check for the file header, it might be PDF or PS with the wrong extension. 
ycaihua/skim-app,WoLpH/skim,WoLpH/skim,ycaihua/skim-app,ycaihua/skim-app,ycaihua/skim-app,WoLpH/skim,ycaihua/skim-app,WoLpH/skim,WoLpH/skim