设置默认的打印机及打印纸，在打印机中设置纸张类型。

Set the default printer and printing paper, paper type in the printer Settings.

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这里使用了默认值调用FPDF（）这个构造器：纸张类型为A4，计量单位为毫米。

The FPDF() constructor is used here with the default values: pages are in A4 portrait and the unit of measure is millimeter.

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