I'm in a little over my head here and was hoping I could get some help. I've created a macro that will go down column in Excel, find the folder it is in, and combine three pdfs whos names are in the current excel file. This part works perfectly fine, but I want to finish this off by converting the pdf to grayscale to remove the color in one of the files. Here is my code:

Sub Reports()
    Dim AcroApp As Acrobat.CAcroApp
    Dim Part1Document As Acrobat.CAcroPDDoc
    Dim Part2Document As Acrobat.CAcroPDDoc
    Dim Part3Document As Acrobat.CAcroPDDoc
    Dim dsheet As Worksheet
    Dim numPages As Integer
    Dim directoryf As String
    Dim i As Integer
     i = 7
    
    Set dsheet = ActiveWorkbook.Sheets(1)
    Set AcroApp = CreateObject("AcroExch.App")
    Set Part1Document = CreateObject("AcroExch.PDDoc")
    Set Part2Document = CreateObject("AcroExch.PDDoc")
    Set Part3Document = CreateObject("AcroExch.PDDoc")
    
    
    Do While dsheet.Cells(i, 1) <> ""
    directoryf = "S:\Month End Reports\2013\Fiscal Period end 05-20-2013\"
    directoryf = directoryf & Dir(directoryf & dsheet.Cells(i, 1) & "*", vbDirectory) & "\"
    
        Part1Document.Open (directoryf & Dir(directoryf & dsheet.Cells(2, 1) & "*.pdf"))
        Part2Document.Open (directoryf & Dir(directoryf & dsheet.Cells(3, 1) & "*.pdf"))
        Part3Document.Open (directoryf & Dir(directoryf & dsheet.Cells(4, 1) & "*.pdf"))
        ' Insert the pages of Part2 after the end of Part1
        numPages = Part1Document.GetNumPages()
    
        If Part1Document.InsertPages(numPages - 1, Part2Document, 0, Part2Document.GetNumPages(), True) = False Then
          MsgBox "Cannot insert pages for " & dsheet.Cells(i, 1)
        End If
        numPages = Part1Document.GetNumPages()
        If Part1Document.InsertPages(numPages - 1, Part3Document, 0, Part3Document.GetNumPages(), True) = False Then
            MsgBox "Cannot insert pages for " & dsheet.Cells(i, 1)
        End If
        
        If Part1Document.Save(PDSaveFull, "H:\test\" & dsheet.Cells(i, 1) & " Yardi.pdf") = False Then
           MsgBox "Cannot save the modified document for " & dsheet.Cells(i, 1)
         End If
        
        Part1Document.Close
        Part2Document.Close
        Part3Document.Close
        i = i + 1
    Loop
    
    AcroApp.Exit
    Set AcroApp = Nothing
    Set Part1Document = Nothing
    Set Part2Document = Nothing
    Set Part3Document = Nothing 
End Sub
This all works fine, but I want there to be no color in the final product as well. I've combed through the Acrobat API, and haven't found anything. Any help would be greatly appreciated.