Import PDF Files as PIMCORE assets via API

I’m importing PDF Files as PIMCORE assets via the API. Like documented here https://pimcore.com/docs/6.x/Development_Documentation/Assets/Working_with_PHP_API.html.

Is

$newAsset = new Pimcore\Model\Asset\Document();
...
$newAsset->setData(file_get_contents("some-file.pdf"));
...

the correct way for importing PDF files to assets via API? When I do this, there are some cryptic 0 byte files created in my root folder (named only “W” or “wv” or something else)? Really strange.