How to change template for multiple items

Question

There are many PDF files in our project that are manually added to the media library.

I see that some of them have the template - /sitecore/templates/System/Media/Versioned/Pdf and some others - /sitecore/templates/System/Media/Unversioned/Pdf

1. Why does this happen. I'm sure the author would not select any settings to have it uploaded as 'Versioned'.And this happend with image files too.

2. I would like to change all versioned pdf to unversioned pdf.

When I try this power shell script, it throws an error:

$master = [Sitecore.Configuration.Factory]::GetDatabase("master");
$entryTemplate = $master.Templates["/sitecore/templates/System/Media/Unversioned/Pdf"];
cd master:"\media library\Files\Test";
Get-ChildItem -recurse | ForEach-Object { if ($_.TemplateName -eq "Pdf") { $_.ChangeTemplate($entryTemplate) } };

Exception calling "ChangeTemplate" with "1" argument(s): "Value cannot be null. Parameter name: template" At line:8 char:76 + ... ($.TemplateName -eq "Pdf") { $.ChangeTemplate($entryTemplate) } }; + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : NotSpecified: (:) [], MethodInvocationException + FullyQualifiedErrorId : ArgumentNullException

Exception calling "ChangeTemplate" with "1" argument(s): "Value cannot be null. Parameter name: template" At line:8 char:76 + ... ($.TemplateName -eq "Pdf") { $.ChangeTemplate($entryTemplate) } }; + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : NotSpecified: (:) [], MethodInvocationException + FullyQualifiedErrorId : ArgumentNullException

Using Sitecore 8.2 update 3

Answer 1

First, wrap your media library test files path with " characters.

Then instead of passing the whole path to $master.Templates:

$master.Templates["/sitecore/templates/System/Media/Unversioned/Pdf"];

use only template specific subpath

$master.Templates["System/Media/Unversioned/Pdf"];