Which is the correct path for a hyperlink in an ArcMap Table?

I am having problems making the hyperlink tool open a hyperlink with a relative path in ArcMap 10.7.

The relative path to the pdf file is in a table joined by a "relate" to a polygon feature class in a FGDB. The Hyperlink setting is set to script with the following code: "PDF" is the field name.

Function OpenLink ( [PDF] )
 Dim path
 Dim objShell
 path = [PDF]
 Set objShell = CreateObject("Shell.Application")
 objShell.ShellExecute path, "", "", "open", 1
End Function

I can successfully open the hyperlink in the info window using the yellow hyperlink tool when the PDF file is saved in the same directory as the MXD but when the PDF file is moved to a directory i.e ../PDF/document.pdf ArcMap does not recognise it as a hyperlink.

I have tried all the following formats with and without quotation marks in the table.

   ../PDF/document.pdf
   /PDF/document.pdf
   PDF/document.pdf

What am I doing wrong?