具体报错信息如下：
[email protected]:~/Documents/GMT$ xpdf global.pdf
Warning: Cannot convert string "-*-helvetica-medium-r-normal--12-*-*-*-*-*-iso8859-1" to type FontStruct
Warning: Cannot convert string "-*-courier-medium-r-normal--12-*-*-*-*-*-iso8859-1" to type FontStruct
Warning: Cannot convert string "-*-times-bold-i-normal--20-*-*-*-*-*-iso8859-1" to type FontStruct
Warning: Cannot convert string "-*-times-medium-r-normal--16-*-*-*-*-*-iso8859-1" to type FontStruct
感觉可能是字体的问题，请假大侠们，如何解决？谢谢