Add-PSSnapin Microsoft.Sharepoint.Powershell
 $SiteURL = "http://sp/sites/sp13"
 $LibraryName ="Documents"
 $DownloadPath ="C:\temp"
 Function Download-SPFolder($SPFolderURL, $DownloadPath)
 {
      Try {
          $SPFolder = $web.GetFolder($SPFolderURL)
          Write-host $SPFolder
          $DownloadPath = Join-Path $DownloadPath $SPFolder.Name 
          If (!(Test-Path -path $DownloadPath))
          {   
              $LocalFolder = New-Item $DownloadPath -type directory
          }
          #Loop through each file in the folder and download it to Destination
          ForEach ($File in $SPFolder.Files)
          {
              #Download the file
              $Data = $File.OpenBinary()
              $FilePath= Join-Path $DownloadPath $File.Name
              [System.IO.File]::WriteAllBytes($FilePath, $data)
              Write-host -f Green "`tDownloaded the File:"$File.ServerRelativeURL        
          }
          #Process the Sub Folders & Recursively call the function
          ForEach ($SubFolder in $SPFolder.SubFolders)
          {
              If($SubFolder.Name -ne "Forms")
              {
                  #Call the function Recursively
                  Download-SPFolder $SubFolder $DownloadPath
              }
          }
      }
      Catch {
          Write-host -f Red "Error Downloading Document Library:" $_.Exception.Message
      } 
 }
 #Main Function
 Function Download-SPDocumentLibrary($SiteURL, $LibraryName, $DownloadPath)
 {
      Try {
          #Get the  Web
          $Web = Get-SPWeb $SiteURL
          #Delete any existing files and folders in the download location
          If (Test-Path $DownloadPath) {Get-ChildItem -Path $DownloadPath -Recurse| ForEach-object {Remove-item -Recurse -path $_.FullName }}
          #Get the document Library to Download
          $Library = $Web.Lists[$LibraryName]
          Write-host -f magenta "Downloading Document Library:" $Library.Title
          #Call the function to download the document library
          Download-SPFolder -SPFolderURL $Library.RootFolder.Url -DownloadPath $DownloadPath
          Write-host -f Green "*** Download Completed  ***"
      }
      Catch {
          Write-host -f Red "Error Downloading Document Library:" $_.Exception.Message
      } 
 }
 Download-SPDocumentLibrary $SiteURL $LibraryName $DownloadPath