If you are familiar with the Crystal object libraries it is simply a matter of setting the ExportOptions and calling the Export method. The following is pretty basic but should help get you started.
Code:
Dim crApp As CRAXDRT.Application
Dim crRep As CRAXDRT.Report
Set crApp = New CRAXDRT.Application
Set crRep = crApp.OpenReport("C:\report1.rpt")
crRep.DisplayProgressDialog = False
With crRep.ExportOptions
.FormatType = crEFTPortableDocFormat
.PDFExportAllPages = True
.DestinationType = crEDTDiskFile
.DiskFileName = "C:\Export.pdf"
End With
crRep.Export False