Thanks for so fast answer 
Yet it solve only part of my problem. It finally prints out my report but it prints all the records not just the one selected by the checkboxes. And before printing it asks me about parameter value.
So my current code looks like that right now:
Code:
Private Sub Print_Click()Dim strDefaultPrinter As String
' get current default printer.
strDefaultPrinter = Application.Printer.DeviceName
' switch to printer of your choice:
Set Application.Printer = Application.Printers("CutePDF Writer")
Me.Recalc
DoCmd.OpenReport "Labels", , , "PrintChk=True"
'Here i tried to count selected checkboxes and print report form them
'If Me!txtCount = 0 Then
'MsgBox "Select a record to print.", vbOKOnly, "Error"
'Else
'DoCmd.Close acReport, "Labels", acSaveNo
'End If
' Switch back to original default printer
Set Application.Printer = Application.Printers(strDefaultPrinter)
Exit Sub
End Sub