$wdStory = 9
$wdMove = 0

$objWord = New-object -comobject Word.Application
$objWord.Visible = $True

$objDoc = $objWord.Documents.Open("c:\temp\test.docx")

$objSelection = $objWord.Selection
$a = $objSelection.EndKey($wdStory, $wdMove)
$objSelection.TypeParagraph()
$objSelection.TypeParagraph()
$text = "This text appended"
$objSelection.TypeText($text)

$objDoc.Save()
$objDoc.Close()
$objWord.quit()

[System.Runtime.Interopservices.Marshal]::ReleaseComObject($objDoc) | Out-Null
[System.Runtime.Interopservices.Marshal]::ReleaseComObject($objWord) | Out-Null