Finding matching PDF files in different folders and merging the two files into one
I cannot do full test as I do not have that PDF software of yours. But the idea is that process all file names in that folder 1, store them in a collection, also if the file name ends with " SomeWord.pdf" then add to another collection.

When done, process the other collection and see if a matched " AnotherWord 2014.pdf" found in first collection. Merge if found.

Reworked after Trial is downloaded.

Option Explicit

Private oFullList As Object, oMyList As Object, oFSO As Object

Private Const FDR1 = "C:\Test\"
Private Const FDR2 = "C:\Test\Merged\"

Private Const sAppend1 = " SomeWord.pdf"
Private Const sAppend2 = " AnotherWord 2014.pdf"

Private oPDF As New PDF_reDirect_v25002.Batch_RC_AXD
Private lFiles As Long

Sub Main()
    lFiles = 0
    Debug.Print Now &amp; vbTab &amp; "Program Started"
    '===[ Create Collection Objects ]===
    ' FullList stores all the filenames in the directory
    If oFullList Is Nothing Then
        Set oFullList = CreateObject("System.Collections.ArrayList") ' Create if not created
    Else
        oFullList.Clear ' Remove all old entries
    End If
    ' MyList only stores filenames that will be checked for merge
    If oMyList Is Nothing Then
        Set oMyList = CreateObject("System.Collections.ArrayList") ' Create if not created
    Else
        oMyList.Clear
    End If
    '===[ Check FileSystemObject ]===
    If oFSO Is Nothing Then
        Set oFSO = CreateObject("Scripting.FileSystemObject")
    End If
    '===[ Main procedures ]===
    CheckFiles
    'ListFiles ' Skipped, debug only
    ProcessMergeFiles
    '===[ Clean Up ]===
    Set oFullList = Nothing
    Set oMyList = Nothing
    Set oFSO = Nothing
    Set oPDF = Nothing
    '===[ Print Summary ]===
    Debug.Print Now &amp; vbTab &amp; "Program Finished. " &amp; lFiles &amp; " merged PDFs has been created"
End Sub

Private Sub CheckFiles()
    Dim oFDR As Object, oFile As Object, sTmp As String, n As Long
    '===[ Process all filenames of FDR1 ]===
    For Each oFile In oFSO.GetFolder(FDR1).Files
        sTmp = oFile.Name
        ' Add to FullList collection
        oFullList.Add sTmp
        ' Only add to MyList collection if it ends with sAppend1
        n = InStr(1, sTmp, sAppend1, vbTextCompare)
        If n &gt; 0 Then
            oMyList.Add Left(sTmp, n - 1) ' Stores only the prefix
        End If
    Next
End Sub

Private Sub ListFiles()
    Dim i As Long
    Debug.Print "=== Listing " &amp; oMyList.Count &amp; " item(s) in oMyList ==="
    For i = 0 To oMyList.Count - 1
        Debug.Print i + 1 &amp; vbTab &amp; oMyList(i)
    Next
End Sub

Private Sub ProcessMergeFiles()
    Dim i As Long, sTmp As String
    For i = 0 To oMyList.Count - 1
        sTmp = oMyList(i)
        If oFullList.Contains(sTmp &amp; sAppend2) Then
            'Debug.Print "Merge file pair found: """ &amp; sTmp &amp; """"
            MergeFiles sTmp
        End If
    Next
End Sub

Private Sub MergeFiles(sFilePrefix As String)
    Dim bSuccess As Boolean
    Dim aFiles() As String ' &lt;- Required datatype

    If oPDF Is Nothing Then
        Set oPDF = New PDF_reDirect_v25002.Batch_RC_AXD
    End If

    ReDim aFiles(1)
    aFiles(0) = FDR1 &amp; sFilePrefix &amp; sAppend1
    aFiles(1) = FDR1 &amp; sFilePrefix &amp; sAppend2

    With oPDF
        bSuccess = .Utility_Merge_PDF_Files(FDR2 &amp; "\" &amp; sFilePrefix &amp; sAppend2, aFiles)
        If bSuccess Then
            Debug.Print "Merged pdf files with prefix """ &amp; sFilePrefix &amp; """"
            lFiles = lFiles + 1
        Else
            Debug.Print "Failed to merge pdf files with prefix " &amp; sFilePrefix
            Debug.Print "ERR(" &amp; .LastErrorNumber &amp; "):" &amp; .LastErrorDescription
            .Reset_Errors
        End If
    End With
End Sub