silverstripe-dms/docs/en/creating-documents.md

Creating documents

Create by relative path:

$dms = DMS::getDMSInstance();
$doc = $dms->storeDocument('assets/myfile.pdf');

Create from an existing File record:

$dms = DMS::getDMSInstance();
$file = File::get()->byID(99);
$doc = $dms->storeDocument($file);

Note: Both operations copy the existing file.