Thanks for the suggestion to break it down and find the problem - see the tree in the forest so to speak.

Here's what solved it...

Set the string value from excel before opening the word application. Also, I didn't need .text at the end...

Here's the final code for those reading along.
Thanks again for your help and this forum.

[VBA]Sheets("Pin_Index").Select
xlvalString = Sheets("Doc_Index").Range("F1")


'Open Word Instance
Set wdApp = CreateObject("Word.Application")
wdApp.Visible = True

'Open Template as Document
wdApp.Documents.Add Template:=(pinString)
wdApp.Activate

'Prefill Data

With wdApp.ActiveDocument
.FormFields("docCategory").Result = xlvalString
End With

[/VBA]