Search for pdf files by date or title

the more i look at this the more i can see issues moving forward
its always going to hiccup when some sort of naming issues pops up

if you accidentally put a pdf in that folder that shouldnt be there

so

                If j = 4 Then
                    On Error Resume Next
                    InvNum = Mid(strFileName, pos + 2) 'inv num - date.pdf
                    Cells(i, 4).Value = DateValue(Trim(Replace(Right(InvNum, Len(InvNum) - InStr(InvNum, "-") - 1), ".pdf", ""))) 'Date minus the .pdf
                    Cells(i, 3).Value = Left(InvNum, InStr(InvNum, "-") - 1) 'extract Inv Num
                ElseIf j = 3 Then
                    On Error Resume Next
                    Cells(i, 4).Value = DateValue(Replace(Mid(strFileName, pos + 2, Len(strFileName)), ".pdf", ""))
                End If

i think your best option is to put an on error resume code in there so it just skips the issue file
it wont fix it but you if you cant control the file names of the pdf this is the next best thing

also it seems case is a problem for you
so amending the search term

    strSearch = UCase(Range("B4").Value) 'search term
        
    Do While strFileName <> vbNullString 'loop for filenames in folder
            
        If InStr(UCase(strFileName), UCase(strSearch)) > 0 Then 'if search term found in filename then go ahead

should help that
mind you if you just search for p d o r F
it will return everything because...well .pdf