Merging 2 PDF's VBA

Hi guys, trying to get this code to work. I have 2 PDF's I want to merge into 1 PDF, then save this "Merged PDF" to a separate location. Keep getting user defined-type not defined error.

Sub Merge()

Dim gPDDoc1 As AcroPDDoc
Dim gPDDoc2 As AcroPDDoc
'Dim gPDDOC3 As AcroPDDoc

Set gPDDoc1 = CreateObject("Title Page.PDDoc")
Set gPDDoc2 = CreateObject("TEST PDF.PDDoc")
'Set gPDDOC3 = CreateObject("AcroExch.PDDoc")
 
chk1 = gPDDoc1.Open("S:\Folder\Title Page.pdf")
chk2 = gPDDoc2.Open("S:\Folder\TEST PDF.pdf")
'chk3 = gPDDOC3.Open("C:\test\test3.pdf")
 
mergefile = gPDDoc1.InsertPages(0, gPDDoc2, 1, 2, 3)
'mergefile = gPDDoc1.InsertPages(1, gPDDOC3, 0, 1, 0)
 
savemergefile = gPDDoc1.Save(1, "K:\Folder2\MERGED.pdf")

End Sub

Anyone know how to fix this?
Thanks