Start by selecting the sheets you want to combine:
ThisWorkbook.Sheets(Array("Sheet1", "Sheet2")).Select
ActiveSheet.ExportAsFixedFormat Type:=xlTypePDF, Filename:= _
"C:\tempo.pdf", Quality:= xlQualityStandard, IncludeDocProperties:=True, _
IgnorePrintAreas:=False, OpenAfterPublish:=True