I cannot control PDFtk through VBA code

I am using PDFtk Server but not for passwords, so I haven't done this exact thing. But your code looks correct. How about the data? If you have spaces in your paths this won't work. You need to quote the strings. It's easy to try this change:

ShellCmd = PDFtkPath & " """ & InputFilePath & """ output """ & OutputFilePath & """ user_pw " & Password

Can you either

Attach the file (see yellow banner at the top of the page)

or

show all your code

see here the VBA code tested; many thanks

Sub Protectpdf()
    Dim PDFtkPath As String
    Dim InputFilePath As String
    Dim OutputFilePath As String
    Dim Password As String
    Dim ShellCmd As String

    ' Path to the PDFtk executable
  PDFtkPath = "C:\Program Files (x86)\PDFtk\bin\Pdftkxp.exe"
    
    ' Path to the input PDF file
    InputFilePath = "D:\Test\input.pdf"
    ' Path to the output PDF file (password protected)
    OutputFilePath = "D:\Test\output.pdf"
    
    
    ' Password for the PDF file
    Password = "090046"

    ' Assemble the command to password protect the PDF using PDFtk
    
    ShellCmd = PDFtkPath & " " & InputFilePath & " output " & OutputFilePath & " user_pw " & Password
    
    'alternative syntax not working:
    'ShellCmd = Chr(34) & PDFtkPath & Chr(34) & " " & Chr(34) & InputFilePath & Chr(34) & " output " & Chr(34) & OutputFilePath & Chr(34) & " user_pw " & Password
        
    'or, another one not working:
    'ShellCmd = PDFtkPath & " """ & InputFilePath & """ output """ & OutputFilePath & """ user_pw " & Password

    
    ' Use the Shell function to execute the PDFtk command
    Shell ShellCmd, vbHide

    MsgBox "PDF file has been password protected and saved to " & OutputFilePath
End Sub

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Welcome to the forum.

We would very much like to help you with your query, however we recommend that you include code tags around your code.

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I did it for you because you are a new member.

You are calling the Windows version of the app. You need to use the Server for line commands. Change your line of code to this:

  PDFtkPath = "C:\Program Files (x86)\PDFtk Server\bin\pdftk.exe"

You still need to use my version of the shell call with the quotes if you have any spaces in the file path. I would recommend you do it anyway.

    ShellCmd = PDFtkPath & " """ & InputFilePath & """ output """ & OutputFilePath & """ user_pw " & Password

Glad to hear it was solved. I gave you the PDFtk path as it is installed on my machine. Maybe yours is different.

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