Delete Annotations
To remove an annotation from a document.
NSURL *url = [NSURL fileURLWithPath:pdfPath];
CPDFDocument *document = [[[CPDFDocument alloc] initWithURL:url] autorelease];
CPDFPage *page = [document pageAtIndex:0];
CPDFAnnotation *annotation = [[page annotations] objectAtIndex:0];
[page removeAnnotation:annotation];