配置测量属性 ​

// 获取需要创建便签的页面对象
CPDFPage *page = [document pageAtIndex:0];

// 创建直线注释
CPDFLineAnnotation *anotation = [[CPDFLineAnnotation alloc] initWithDocument:document];

// 设置起点和终点
anotation.startPoint = CGPointMake(350, 270);
anotation.endPoint = CGPointMake(260, 370);

// 创建测量属性,设置测量比例与精度 (默认比例 1 cm = 1 cm)
CPDFDistanceMeasureInfo *measureInfo = [[CPDFDistanceMeasureInfo alloc] init];
measureInfo.rulerBase = 1.0;
measureInfo.rulerBaseUnit = [CPDFMeasureConstants sharedInstance].cpdfCm;
measureInfo.rulerTranslate = 1.0;
measureInfo.rulerTranslateUnit = [CPDFMeasureConstants sharedInstance].cpdfKm;

// 设置精度为 0.01。
measureInfo.precision = [CPDFMeasureConstants sharedInstance].precisionValueTwo;

// 设置两端引线长度（此属性CPDFDistanceMeasureInfo独有）
measureInfo.leadLength = 5.0；

// 设置直线注释的测量属性
//设置MeasureInfo:相关信息需要在将其加在页面后才会有效
[anotation setMeasureInfo:measureInfo];

// 更新注释外观使其显示在文档上
[page addAnnotation:anotation];