试试
Dim Book As New XLS.Book(ProjectPath & "Attachments\添加订单.xls")
Dim fl As String = ProjectPath & "Reports\添加订单.xls"
Book.Build() '生成细节区
Book.Save(fl) '保存工作簿
Dim App As New MSExcel.Application
Dim Wb As MSExcel.WorkBook = App.WorkBooks.Open(fl)
wb.ExportAsFixedFormat(MSExcel.XlFixedFormatType.xlTypePDF, fl)
App.Quit