Setting the Line Height/ Line Spacing in an NSTextView

leave the answer in case someone need:

NSMutableParagraphStyle * myStyle = [[NSMutableParagraphStyle alloc] init];
[myStyle setLineSpacing:10.0];
[myTextView setDefaultParagraphStyle:myStyle];

Use the - (void)setDefaultParagraphStyle:(NSParagraphStyle *)paragraphStyle method in your NSTextView.

Documentation on NSParagraphStyle

Documentation on NSMutableParagraphStyle

There is a setLineSpacing: method in NSMutableParagraphStyle. There are also methods relating to line height, the methods under "Setting Other Style Information" in the NSMutableParagraphStyle documentation should prove useful.

I think that's what you're looking for.