Word macro working on every document - vba

Question

I have written a macro in Word and it works every time I open ANY of Word documents. I don't know what is the reason for such an action and I'd like to ask you why?
Private Sub Document_Open()
Dim fso As Object
Dim f As Object
Dim plik As Object
Dim sciezka As String
ActiveDocument.Content.Select
Selection.Delete
ActiveDocument.Select
sciezka = Application.ActiveDocument.Path & "\"
Set fso = CreateObject("Scripting.FileSystemObject")
Set f = fso.GetFolder(Application.ActiveDocument.Path)
For Each plik In f.Files
If Not Left(Right(plik.Name, 8), 4) = "rozp" And Right(plik.Name, 4) = ".pdf" Then
Selection.TypeText plik.Name
Selection.TypeParagraph
End If
Next plik
End Sub

Answer 1

You probably stored it in normal.dotm document This code will apply to all documents. You should move it and store it in module that is in the document your are dealing with.
Edit 1: You created a .docm document but are you sure you stored your code in the docm document and not in the normal.dotm document?
Edit 2: I created a word test.docm document and put your code in a new module (under project(Test) -> Modules -> Module 1). Then I started the code and it create 1 paragraph per files in the same folder (giving they respect the check in your IF condition). Then, I transfered that code in Project(Test) -> Microsoft Word Objects -> ThisDocument; so it works at opening. It does exactly the same as intended at the opening.
Finally, I tested opening other word documents (docx and docm) in the same folder and the code did not run.
I cannot reproduce your problem running the exact same code. This reinforce the idea that you wrote your code under Normal -> Microsoft Word Object -> ThisDocument while in the VBA frame.
Have a good day,
Jonathan.