findandreplacestringindocx.ps1

$list = gci "C:\MyDocs" -Include *.docx -Force -recurse
foreach ($foo in $list) {

$objWord = New-Object -ComObject word.application
$objWord.Visible = $True

$objDoc = $objWord.Documents.Open("$foo")
$objSelection = $objWord.Selection

$findtext= "String to Find"
$ReplaceText = "Replace with String"

$ReplaceAll = 2
$FindContinue = 1
$MatchFuzzy = $False
$MatchCase = $False
$MatchPhrase = $false
$MatchWholeWord = $True
$MatchWildcards = $True
$MatchSoundsLike = $False
$MatchAllWordForms = $False
$Forward = $True
$Wrap = $FindContinue
$Format = $False

$objSelection.Find.execute(
        $FindText,
        $MatchCase,
        $MatchWholeWord,
        $MatchWildcards,
        $MatchSoundsLike,
        $MatchAllWordForms,
        $Forward,
        $Wrap,
        $Format,
        $ReplaceText,
        $ReplaceAll
    )
}