excelguy. Your problem can be solved using object-oriented approach.
In the separate class module let's create a class (let's say name it "clsExportPosition"). This class should contain two attributes:
- "DestinationFile" - contains full path to appropriate pdf-file.
- "TargetWorksheets" - collection of worksheet names affiliated to this   pdf-file.
Code listing of this class module as follows:
Private pvtDestFile As String
    Public TargetWorksheets As New Collection
    Property Get DestinationFile() As String
          DestinationFile = pvtDestFile
    End Property
    Property Let DestinationFile(newValue As String)
          pvtDestFile = newValue
    End Property
    Public Sub AddTargetWorksheet(wrkShtName As String)
          TargetWorksheets.Add wrkShtName
    End Sub
Save this class module with name clsExportPosition in your workbook. Then we'll rewrite your code as follows:
'This is main routine which forms object collection. 
'Each object in this collection will contain pdf-filename (full path) in one 'attribute and list of affiliated worksheets in another attribute. Finally 
'this routine calls subroutine performing export to pdf format
Private Sub CreatePDF_Button_Click()
         Dim i As Long
         Dim ExportPositions As New Collection
         Dim LastRow As Long
         With ActiveWorkbook.Worksheets("PDF_Management")
             LastRow = .Cells(Rows.Count, 1).End(xlUp).Row
             Call AddExpPosition(.Cells(2,1), .Cells(2,3) & "\" & .Cells(2,2), ExportPositions)
             For i=3 To LastRow
                  If IsDestAlreadyPresent(.Cells(i,3) & "\" & .Cells(i,2), ExportPositions) Then
                        Call AddSheetToList(.Cells(i,1),  .Cells(i,3) & "\" & .Cells(i,2), ExportPositions)
                  Else
                        Call AddExpPosition(.Cells(i,1),  .Cells(i,3), & "\" & .Cells(i,2), ExportPositions)
                  End If
              Next i
         End With
         Call CreatePDF(ExportPositions)
    End Sub
'== These are auxiliary subroutines and functions==
    Sub AddExpPosition(pgName As String, pthName As String, expCollection As Collection)
       Dim exPosition As New clsExportPosition
       exPosition.DestinationFile = pthName
       exPosition.AddTargetWorksheet(pgName)
       expCollection.Add exPosition
    End Sub
    Sub AddSheetToList (pgName As String, pthName As String, expCollection As Collection)
        For Each itm In expCollection
             If itm.DestinationFile = pthName Then
                   itm.AddTargetWorksheet(pgName)
             End If
       Next
    End Sub
    Function IsDestAlreadyPresent(pthName As String, expColl As Collection) As Boolean
         Dim result As Boolean
         result = False
          For Each itm In expColl
              If itm.DestinationFile = pthName Then
                      result = True
              End If
          Next itm
          IsDestAlreadyPresent = result
    End Function
    Function expCollToArr(expCollect As Collection) As Variant
         Dim result As Variant
         Dim cnt As Long
         ReDim result(expCollect.Count -1)
         For cnt = 0 To expCollect.Count - 1
              result(cnt) = expCollect(cnt +1)
         Next
         expCollToArr = result
    End Function
    Sub CreatePDF(expCollection As Collection)
          Dim destArr As Variant
          For Each expItem In expCollection
                destArr = expCollToArr(expItem.TargetWorksheets)
                ActiveWorkbook.Sheets(destArr).Select
                ActiveWorkbook.Worksheets(destArr).ExportAsFixedFormat Type := xlTypePDF,_
                Filename := expItem.DestinationFile,_ 
                ignoreprintareas := False,_ 
                openafterpublish := False
         Next
    End Sub
That's it. Just paste this code into VB editor in your workbook, save it and try to play with. Hope it helps.