Talk is cheap, show me the code!
NSError *error;
NSString *regexStr = @"href\\s*=\\s*([\'\"\\s]([^\"\']*\\.(?:doc|docx|ppt|pptx|xls|pdf.html|pdf|xlsx))[\'\"])";
NSRegularExpression *attachmentExpression = [NSRegularExpression regularExpressionWithPattern:regexStr
options:NSRegularExpressionCaseInsensitive error:&error];
content = [attachmentExpression stringByReplacingMatchesInString:content
options:0
range:NSMakeRange(0, [content length])
withTemplate:@"href='javascript:void(0);' onclick='myHandler($1)'"];