Inconsistent page count of a PDF document - pdf

Question

I'm trying to get the number of pages in the PDF document. Some of my PDFs are created in Word (saved as PDF), some of them are Xeroxed into the directory (not sure if this matters).
After hours of research I've come to find out that this is easier said than done. The page count rarely comes back giving me the correct number of pages, even though most PDF's do in fact have /Count inside the Binary Code.
For example I've used the following code; it is supposed to open the document in Binary Mode, look for /Count or /N and get the number next to it which is supposed to give me the page count.
Public Sub pagecount(sfilename As String)
On Error GoTo a
Dim nFileNum As Integer
Dim s As String
Dim c As Integer
Dim pos, pos1 As Integer
pos = 0
pos1 = 0
c = 0
' Get an available file number from the system
nFileNum = FreeFile
'OPEN the PDF file in Binary mode
Open sfilename For Binary Lock Read Write As #nFileNum
' Get the data from the file
Do Until EOF(nFileNum)
Input #1, s
c = c + 1
If c <= 10 Then
pos = InStr(s, "/N")
End If
pos1 = InStr(s, "/count")
If pos > 0 Or pos1 > 0 Then
Close #nFileNum
s = Trim(Mid(s, pos, 10))
s = Replace(s, "/N", "")
s = Replace(s, "/count", "")
s = Replace(s, " ", "")
s = Replace(s, "/", "")
For i = 65 To 125
s = Replace(s, Chr(i), "")
Next
pages = Val(Trim(s))
If pages < 0 Then
pages = 1
End If
Close #nFileNum
Exit Sub
End If
'imp only 1000 lines searches
If c >= 1000 Then
GoTo a
End If
Loop
Close #nFileNum
Exit Sub
a:
Close #nFileNum
pages = 1
Exit Sub
End Sub
However, most of the time, it defaults to pages = 1 (under a:).
I've also updated this to 10000 to be sure that it hits the /Count line, yet it still does not give me the correct count.
If c >= 10000 Then
GoTo a
End If
I also came across this reddit
Is there another way to do this, something I can utilize in my app?
Any help is greatly appreciated.
Background:
This is for a legacy vb6 app where I'm attempting to let the user manipulate the PDF files. I added a ListBox that displays all PDF documents in a particular directory. When user double clicks on any one of the files, i display it in a WebBrowser component inside my application.
EDIT: Image containing the BinaryMode line Count for 3 different documents:
I double checked the page count, and /Count displays the correct page count for each of the three documents.

Answer 1

Regular expressions have limits, but I prefer to use them for searching for strings and I think this would be a good place to use one. You may want to play with the pattern because I did this relatively quickly with only a little testing.
Add a reference to Microsoft VBScript Regular Expressions 5.5 to your project. Then you can try the sample code below.
Private Sub Command1_Click()
Dim oRegEx As RegExp
Dim fHndl As Integer
Dim sContents As String
Dim oMatches As MatchCollection
On Error GoTo ErrCommand1_Click
'Open and read in the file
fHndl = FreeFile
Open some pdf file For Binary Access Read As fHndl
sContents = String(LOF(fHndl), vbNull)
Get #fHndl, 1, sContents
Close #fHndl 'We have the file contents so close it
fHndl = 0
'Instantiate and configure the RegEx
Set oRegEx = New RegExp
oRegEx.Global = True
oRegEx.Pattern = "((?:/Count )(\d+))"
Set oMatches = oRegEx.Execute(sContents)
'Look for a match
If oMatches.Count > 0 Then
If oMatches(0).SubMatches.Count > 0 Then
MsgBox CStr(oMatches(0).SubMatches(0)) & " Pages"
End If
End If
Exit Sub
ErrCommand1_Click:
Debug.Print "Error: " & CStr(Err.Number) & ", " & Err.Description
If Not oRegEx Is Nothing Then Set oRegEx = Nothing
If Not oMatches Is Nothing Then Set oMatches = Nothing
End Sub
An explanation of the RegEx pattern:
() creates a group
?: inside the parenthesis makes the group non-capturing
<</Linearized is a literal string
.* greedy quantifier, match any character 0 or more times
/N literal string
\d+ greedy qualtifier, match digits 1 or more times
>> literal string