请问
在使用多线程使用PdfDocument.saveToFile()转换pdf时报错
报错信息
class com.spire.office.packages.sprtzja: Item has already been added. Key in dictionary: 'BCDEEE+MicrosoftYaHei-NNCDS' Key being added: 'BCDEEE+MicrosoftYaHei-NNCDS'
com.spire.ms.System.Collections.Hashtable.spr〧┧(jhc:351)
com.spire.ms.System.Collections.Hashtable.addItem(jhc:179)
com.spire.office.packages.sprvbca.spr≌┆—(Unknown Source)
com.spire.office.packages.sprlpw.spr┲…—(Unknown Source)
com.spire.office.packages.sprnly.spr┲…—(Unknown Source)
com.spire.office.packages.spreuea.spr‡┠(Unknown Source)
com.spire.office.packages.spreuea.<init>(Unknown Source)
com.spire.office.packages.sprfyea.spr〧┓—(Unknown Source)
com.spire.office.packages.sprfyea.spr⅓┓—(Unknown Source)
com.spire.office.packages.sprfyea.spr’└—(Unknown Source)
com.spire.pdf.PdfDocumentBase.spr▇⅜(Unknown Source)
com.spire.pdf.PdfDocumentBase.save(Unknown Source)
com.spire.pdf.PdfDocument.saveToFile(Unknown Source)
是因为什么